I'm not very good in the subject of addons, and when I wanted to be able to add a polysphere on blender, I googled around and found an "Add_mesh_round_cube" addon which I believe should be correct. It's on the blender developer website, so I think it's quite a legitimate source:

Apparently this is the python text of the addon. But I don't know how to proceed from here. Can anyone help me out?

• just as a side note, what's wrong with using shift+a, add uv sphere in the 3d viewport? – aliasguru Aug 3 '16 at 19:40
• Possible duplicate of Installing an addon – aliasguru Aug 3 '16 at 19:48
• Alias guru, I want to add polyspheres intead because UV-spheres will pinch detail at the poles, whereas the polysphere has only quads and the detail is all nicely distributed, and it makes for some great topology – Espen Sales Aug 3 '16 at 19:52
• It is included into Extra Objects addon; if you want it separate find it on github. In general, if you see an addon in plane text, select it and save to a file with .py extension. – Mr Zak Aug 3 '16 at 20:00

Select the text and copy it, then paste it into a text editor and save it as something like Add_mesh_round_cube.py (make sure to give it the .py extension). Now you can load it into Blender like any other addon. Open the User Preferences (Ctrl+Alt+U) and go to the Addons tab, then hit Install From File and select the file from your computer. Then click the little checkmark next to it to enable it.