I don't want to sound patronising, but, if you have to ask then it's maybe not for you.
You do it through the edit mode. You will have to take photo's of the sponsors & club badges etc.. using a camera (Xbox vision cam or equivelant.) Then you need to cut round the image and alter any colours that have faded etc..
A standard English club badge can take anything from 10mins to a couple of hours. I.E. Swansea's badge for example is easy. Take the photo, cut round the white circle and you're done. then try doing Coventry, Newcastle, Barnsley, QPR etc. they could take hours.
It also depends what console you're using, the above is mainly for xbox although PC is said to be a lot easier and PS3 you can use .png files.