You will first need to be able to post a diagram here with moves. Once you have made the moves, you can right-click on a specific move to add comments or things like exclamation marks.
Can someone give me a step by step on how to annotate chess.com games?

Abhay (and others who are interested): Here's a step-by-step description I would offer. Try it and if I've inadvertently missed any steps, please let me know and I'll augment/correct my writing below:
1) First, you need a tool that helps to annotate games. There are many such tools (online for free), including Chess.com Live, where you can use the Analysis Board. It does a fairly good and reliable job of helping you to annotate (with some small problems that are easy to fix after that).
2) Assuming we're using the Analysis Board, let's go to it. Go to chess.com/live, then click on the button to the upper right that shows a chessboard icon on it, and from there click on "Analysis Board".
3) If you have a transcribed game (e.g., 1.e4 c5 2.Nf3 d6, etc.) or a position you wish to start to annotate from, you enter that into the box that says FEN / PGN, and click "Start".
If you do not have either of these and simply wish to move the pieces from the very start of a game (e.g., a game you have written on a paper score-sheet before) and annotate as you go, then simply press "Start" while leaving the FEN / PGN box empty.
Note: FEN is a special format for telling a software what position is on the board at a given moment. You can learn about it by looking for "FEN notation" online -- it should be not hard to pick up and do a simple practice on. If you need any help or clarification, just ask and I'll be happy to offer more guidance there.
PGN is the computer file format of an annotated game -- what you will eventually get when you save your game annotations (see below).
4) Now you can navigate through your game in the Analysis Board viewer (move by move or skipping forward/backward as you wish, using the icons provided below the area where the list of moves shows up). When you wish to add some comments to a move, or to indicate the quality of a given move (e.g., "!", "?", "!?", etc.), go to that specific move, right click (I'm assuming you're on a Windows computer/laptop here) and select what specifically you wish to do from the menu that shows. It's fairly self-explanatory.
5) When you wish to save your work (and I recommend doing so often, even if you intend to continue annotating -- just in case, to avoid unnecessary loss of work), click on the downward-pointing arrow icon. It's located to the right of the navigation icons and also to the left of an easily recognizable icon with a rook and a pawn. Also, if you hover over the icons, they should show you hints (called tooltips) of what each is for -- you're looking for the one that shows "Download".
6) After you click that "Download" icon, you have the PGN file of your annotated (up to the time where you clicked) game saved on your computer's hard drive. Where exactly it is, depends on your setup -- but on a Windows computer look in the "Downloads" folder, located under C:\Users\YOURUSERNAME\Downloads.
7) Next time you wish to show this annotated game to someone or continue annotating, you simply upload the game's PGN on the Analysis Board -- by copying the contents of that plain text PGN file into the FEN / PGN box (as I explained above). Then repeat the other steps, as needed.
Let me know if this is clear. I tried to make it error-free.
P.S. At the end of this process, you can send your best annotated game to NW Chess magazine for publication! All they want is your PGN file with your annotations inside.

How can I annotate a currently active game? I see the analysis board and I can click comment before or after and get the "Add a comment" text (see below) but I can't actually type in it. This works fine for completed games but not active ones.

How can I annotate a currently active game? I see the analysis board and I can click comment before or after and get the "Add a comment" text (see below) but I can't actually type in it. This works fine for completed games but not active ones.
You can't annotate a game while playing it...

How can I annotate a currently active game? I see the analysis board and I can click comment before or after and get the "Add a comment" text (see below) but I can't actually type in it. This works fine for completed games but not active ones.
You can't annotate a game while playing it...
There may be a distinction between what type of game is the current one that you wish to annotate. For daily (slow) games you certainly can annotate while still playing -- I do this all the time by adding plenty of variations (and occasionally comments) that I consider as alternatives in the Analysis Board tool. It helps a lot to not have to remember all that while waiting for your opponent to respond (sometimes for days on end).
Can someone give me a step by step on how to annotate chess.com games like where do you go and how do you do it I see a lot of people do it and I want to know how? Thanks!