UV Mapping help

[ilovedividends]

This Car tutorial has a moment an hour in which this link takes you directly there:
http://youtu.be/GQY-4Xz6Kxs?t=1h13m2s

to which he discusses uv mapping.  I am curious how to accomplish this.  I was wondering if someone could comment on how it is done using say a coin.  So you have a coin modeled that is 10mm in diameter.  All I want is a triangle to be "bumped" in the middle causing a depression.

Can you just open up illustrator draw a 10mm 'white' circle with a 'black' triangle in the middle and export it in pixel format and/or use photoshop to dial it in the right format?
Or is there a requirement that you 'unwrap' the coin into some format that you can then draw on using illustrator and then save it out?
3) Is KS just centering the jpeg with the center of the part?

Thanks.