its just not showing up in my add-ons list, even though i can see it in my add-ons folder. i'm not sure what the exact problem is.
If it's not showing up in the add-ons list then it's definitely just not installed properly.
If you've downloaded it multiple times, make sure there's no (2) or anything at the end of it's name. And make sure that you restart the game afterwards.
And make sure you're putting them in the install you're using. If you previously ran the game out of program files but started using the launcher, the place to put them is now in my documents. Or if you've switched over to steam, you'll have to go into the Blockland folder within the steam directory.