Sorry if this is common knowledge by now but I've just recently got back into the game and was looking into mods. My goal was to be able to use Optifine and Forge together in 1.13.2 but no matter what I do Optifine just won't work (as in, I can't use shaders or any of its added settings). Forge, however, seems to be working fine. Any help with this or do the two just not cooperate for this version? Thanks.
I'd say try extracting Optifine when you get to the point of saying what you want to do with Optifine with it's install window. Then put the extracted file into the mods folder. Warning though: 1.12.2 and prior folders work to make the game load mods. 1.13.2 Forge and other modloaders like Rift or Fabric can't read mods inside a deeper folder.
If that doesn't work then someone else will know since I'm not used to Optifine and only use it to do my own testing with it sometimes so I don't use it often. Extracting it I'm used to though, the profile setup I never use with modded environments because I find it never works. Extracting I can have issues with but it's what I'm used to getting working. I'd try going between versions of Optifine if one does work though. Like I've had success with E4 and Rift Modloader (when Forge 1.13/1.13.2 wasn't a thing and Rift was the only modloader out/a bigger deal I guess). And it worked fine. But E5 of Optifine for 1.13.2 has issues and E6 not sure about with my experience. Might work for you though, but just saying it's best to try out just encase.
After a bit of testing of E6 and E4 with Forge 1.13.2 version 44 I can't get it to work so... Maybe make sure Forge is updated or wait until it's stable enough I'd say. Or maybe I just need to check out another Optifine version... Not sure honestly.