I'm convinced that sometimes these mods/maps upload correctly and sometimes they don't. So here is a helpful guide to help you if it doesn't work.

-Locating the map-
When you start to set up a new game and you go to play the Rakhana map, you will go into "Additional maps", and from there you just need to scroll down to find it in the R section. Sometimes we just overlook things :)

-Having problems getting the map to work-
If you're having a problem getting the map to work, follow this easy steps process.

My Documents > My Games > Civilization 5 > Mods > Homeworld Rakhana > Build > Homeworld Rakhana > Rakhana <-- Take this file and move it into the folder 'Maps' which is located in Civilization 5. After that you just need to repeat the 'locating the map' steps.

Hope this helps, if it doesn't please let me know!