1 download the project
2 when you download it it might look like a zip so you have to drag the zip on your desktop and double click the zip and it will turn to a folder
3 locate your minecraft folder at library/application support/ minecraft
4 go to the saves folder in the minecraft folder this is where all your worlds are saved
5 drag the minecraft project folder to the saves folder
6 some times it wont work so you have to got to the minecraft project folder and there will be a folder inside so then put that folder in the minecraft saves folder
7open minecraft find the world and done