Ok. I want to add graphics, not units.
I.e. I want to improve how the base game looks.. I don't need or desire to change the descriptions/stats etc.
How do i simply alter how the units look?
Dude, this is (perhaps accidentally) an oxymoronical statement. Nevertheless, we were all there at some point, so let me see if I can break it down how I understand it. (I am no master, by the way.)
There are three things you raise here. First off, altering unit statistics is the easiest thing to do - you can do all that in the Map Editor. But you don't want to do that.
Second, changing unit descriptions is not so easy. However, you say you are fine with their names and Civilopedia entries (descriptions) already, so I won't go into how one changes those sorts of things.
Thirdly, to your question, if you just want to change unit depictions, then you would have to open up a huge can o' worms, my friend. Let me tell you why, and then you can ask another question as to how, if you are still so interested.
A) Unit depictions are altered by having a full set of .ini, .flc., and .pcx files to replace the ones that you no longer want to replace or want to supplement.
B) The unit folder has to match up with your PediaIcons.txt file, as well as the .ini file within the unit folder with its respective .flc files. (That is, it is rather easy to change the unit depictions in the game menus, but their animations will be based on what you have for their .flc files.)
C) The units_32.pcx file has to have updated graphics for the unit(s), which must match up in the Map Editor.
Long story short, if all you want to do is change how the units look in the game, then you will have to replace or add a number of things first. Luckily for you, there is
www.civfanatics.com to help you out - they have this thing broken down into a simple science for guys like you and me. Read everything in the customization forums before asking more questions - very helpful information awaits you!