Just open SCID vs PC, Open/Create a database, then import the PGN into the database. I don't have the program installed on the system I'm on, but I think the option is under the Tools menu.
PGN file to SCID file

Thanks, but it crashes every time I try to do that. I'm guessing because it has a hard time processing large pgn files. That's why I'm trying to convert it first - in the hopes a scid version won't crash the program.
Is there another fix to the crashes?

I have never had issues in the past importing large PGN files that are truly text only files. Are you sure your file is a PGN? It should be plain text.

Yeah, definitely pgn. It's 1.5 mb. Notepad indicates that it can't open it because it's too large. Some broader issue with my computer?

Notepad can't open very large files. I use Notepad++ for things like that.
Did you get the file online? I could take a look at it and see what might be going on (and try it when I get to my main computer)

Thanks. I ordered it and received it through some equivalent of dropbox. So I can't point to it directly, but is there a good way for me to send it to you?

Thanks, but it crashes every time I try to do that. I'm guessing because it has a hard time processing large pgn files. That's why I'm trying to convert it first - in the hopes a scid version won't crash the program.
Is there another fix to the crashes?
Try Scid-vs-PC 4.20. It has a PGN parsing fix.

Thanks, but it crashes every time I try to do that. I'm guessing because it has a hard time processing large pgn files. That's why I'm trying to convert it first - in the hopes a scid version won't crash the program.
Is there another fix to the crashes?
Try Scid-vs-PC 4.20. It has a PGN parsing fix.
The OP provided me a copy of the file. It appeared to be corrupt; there was a lot of empty data and it choked a lot of programs. I split the file into multiple parts and could only load a few of the portions in a text editor even.
I'm trying to covnert a large PGN file to a SCID file to use in scid vs pc. (The PGN file is too large for the program to load it).
In the command prompt I'm typing this:
"C:\Scid vs PC-4.19\bin\pgnscid.exe" F:\chess\master.pgn C:\Users\TL\Documents\tcl\Chess\Databases (OM CORR)\PGN version\OM Corr 201805 PGN.pgn
And I get this:
C:\Users\TL>"C:\Scid vs PC-4.19\bin\pgnscid.exe" F:\chess\master.pgn C:\Users\TL\Documents\tcl\Chess\Databases (OM CORR)\PGN version\OM Corr 201805 PGN.pgn
C:\Scid vs PC-4.19\bin\pgnscid.exe: create a Scid database from a PGN file.
Usage: C:\Scid vs PC-4.19\bin\pgnscid.exe [-f] [-x] filename.pgn [database]
-f: Force overwrite of existing database.
-x: Ignore comments before games.
Database name defaults to the PGN filename without the ".pgn" suffix.
Note: A Gzip compressed file (e.g. filename.pgn.gz) can be used.
Which looks great -- but then nothing happens. Isn't it supposed to create a scid file? What more do I need to do?