Steinberg's Cubase software can be purchased from many retailers it is not legally available for free.
YOu forgot the important part: How do you use WHAT in Cubase
Cubase 5 is no longer sold or produced due to the release of the newer Cubase 6 and Cubase 7. These newer versions of the software retail for $400 each.
Yes, it is only limited who is allowed to buy it.
Install software and drivers.
Reinstall the software
Use the group tracks
It will install on most Mac computers with an intel processor doesn't matter what model of intel. It just requires a Mac built pretty much after 2006. Will not work on a power series such as a g3-5
Civilization 5 is powered through the Steam system so you will need to install Steam and create an account to install and run the game. (See links below)
You can get Cubase from Steinbergs website
Add a track and press record.
Yes, there is Logic, Garage Band, Cubase, etc. many different varieties of recording softwares on a mac but experiment with some to find which best works for you.