Does anyone know how to install custom levels?
I never knew about them as a kid, but going to it now I am very interested in playing user-created levels since I've played the standard game hundreds of times.

From what I've read, I just need to extract the files in the .zip of the custom level of choice to the jj2 directory.
I have done this for several levels, and NONE of them are showing up aside from the ones that gog included with the game.

can someone please help me? :(

This is indeed all you need to do. The extracted files must be in the same folder as Jazz2.exe and all the other .j2l files, NOT in the "UserLevels" subfolder.

that is what I did though.
None of the levels I added are showing up in the home cooked levels, just the ones that came with this gog release.

Some levels are set by their creators not to appear in the HCL list. Maybe you got really unlucky with your choices? Which levels did you download? Can you show a screenshot of your folder confirming your downloaded levels are in the same folder as Jazz2.exe and Home.j2e?

I figured it out; my game did NOT have the JJ2+ mod installed, I thought it came with this gog release. It did, but it didn't install automatically.

For anyone else with this issue; the installer for the game with the JJ2+ mod is in the game goodies. Or if you're using gog galaxy, you click on the "more" button, then settings. Then where it says "channel" you want to set that to "JJ2+ Mod" and it'll install the mod into the game. All your save files will still be there.