Go to chess.com profile on whom you want to add a friend and you will see this on the left side of the profile:
Friend's Request
It won't let me send friend requests because it says i have 20 pending friend requests. What does this mean and I how can I make it so I don't have 20 pending friend requests?

Maybe basic members are limited on adding friends on the day? I'm not sure, why not contact chess.com staff about this?

@ ColorlessWind: It means you can't send out anymore friend requests (doh!) maybe chess.com doesn't want their server cluttered up with zillions of never-to-be-accepted-or-declined friend requests, in additon to all the other stuff they're cluttered up with, like complete records of members games, blogs, forums, articles, news etc etc.
Start deleting some of your pending fried requests after clicking on "Add to my friends list"
@Roy yeah, that was my first thought, but some of these so-called "pending requests" are actually friends who have already accepted requests! So what do I do?

From the main site you can only send out a max of 20, this doesn't apply in live chess though.
At the moment you have over 70 pending friends requests sent that others haven't yet accepted or declined, so perhaps cancel some of those?
but some of those "pending requests" appear under my friends list whenever I play blitz. There seems to be a bug.

They will.
In live chess the friends list works differently.
If for example you sent me a friend request when in live chess, if i don't accept or decline it my name will still appear on your friend list but where i see your name, it shows me 'Accept' next to it. I wouldn't appear on your homepage friends list though until I actually clicked Accept
How do I send a friend's request?