Whoops sorry I checked and just found that 9,10,&11 are out. To install forge, I used the website to download it and then I pressed the install server button. The contents of start forge.command is:
cd "$(dirname "$0")"
exec java -Xms2G -Xmx2G -jar forge.jar
I renamed the forge file to forge.jar and the server file to MC1.12.2.jar