Every card you can use in Forge has three things: a .txt file that explains what it does that's located in Forge/res/cardsfolder/[a folder you create yourself, for ease of access, that's just for custom cards], a .full.jpg file that shows what it looks like that's located in Forge/cache/pics/[set code], and a .txt file for the set it belongs to that's located in Forge/res/editions/[set name]. If you're trying to use a card in Forge and it's not working properly, you're probably missing one of these three things.

HOW TO USE
To import custom cards into Forge, download the .txt files located here in Database/[origin*]/[set]/cards and put them into a separate folder in Forge/res/cardsfolder, next to cardsfolder.zip. ALSO download the .txt file whose name is the set written in full (ex. A Tourney at Whiterun.txt) and put it in Forge/res/editions. Without that set.txt file, Forge will display custom cards' sets as ???. Download art from Database/[set]/art and put it in Forge/cache/pics/cards/[set code].

* The origins are divided into two main groups: Those sets that are in the MSEM Instigator database, and those Individual cards that aren't, grouped by their designer. For example, /Individual/FLAREdirector contains both .txt and .full.jpg files for cards designed by FLAREdirector. For the most part, it ought to be on the onus of the designer to Forge their own cards, although other people can ask for permission, broadly or on specific cards, to put their cards into this database.

HOW TO CONTRIBUTE
When you're naming your file, ignore apostrophes [ajanis_welcome.txt] and commas [sheoldred_whispering_one.txt], and replace all spaces with underscores _.

Make comments in your files by prefacing them with #.

When you're naming your art file, save it as [name].full.jpg. Write the name out in full, i.e., Portent of the Long Winter.full.jpg.

Most cards can be generated just by cobbling together parts from cards that already exist. Scryfall is your friend! With complex cards, it is highly recommended that you test them yourself in Forge before uploading them here.