How do I add downloaded worlds to minecraft?

Maps are arranged according to date, usually custom maps are near the bottom if you play single player often.

I went to the bottom, its not there. Its not at the top or middle either.

Perhaps you placed the zip/rar file inside instead of the world folder?

sorry but did you mean "note" blocks
.... -_-

also it would help if you mention what type of computer your using, window or mac.
then that would help us help you

if it still dosen't work try these:
https://www.youtube.com/watch?v=oAVq9c-wDYw<- windows
https://www.youtube.com/watch?feature=endscreen&v=BXJimyh3yho&NR=1<- mac

Did you put it in the saves folder? Was it a folder with a data folder, region folder, level, level.dat?

I'm done with this for now.. back to EMC...

Hu

Huh...That's unusual try downloading again, or try extracting it.

Don't give up.
Playing custom maps gives you a whole new experience.
Puzzle maps to test your brain, Pakour maps to test your jumping skills, extreme survival maps where you start with very limited resources, themed maps where a story is told and the popular complete the monument [CTM] maps where all your minecraft skills are challenged.

My recommendation is the original skyblock challenge