Unit install

If I download a mod or new unit how do I ' install ' it in to the game please?

For a mod, most come with an exe that installs it. If not, unpack it into the Mods folder of the game. Assuming that you are asking about the basic game not the Warlord or BTS expansion, that would be the "Mods" folder in the CIV folder where your programs are located, not the one in "My Documents". That is the same folder where you will find the mods that come with the game. Be sure that the mod you download is for vanilla not one of the expansions. Mods intended for the expansions will not work with the basic game. Also be sure that your game is updated to version 1.74 (the last version), since many of the mods will require that.

To add a new unit, you have to do a bit of modding yourself. Having never done that, I will leave it to others to describe.