Go into create a character, their you can customize your character's colors, body, weapons, and abilities.
I don't own this game but I was curious about something. I've heard you can make your own characters. Is it possible to make Wheeljack or something at least close to him?
Not really. Basically, the character customization is taking the body of one TF and colouring it another colour, e.g. Optimus Prime in yellow+green rather than red+blue. Plus with the limited colour pallet (only 5 colours for each faction), you're not really gonna be able to get a good colour match.
You can make Sideswipe look like Tracks and Starscream have the classic colours when disguised. Just colour the Autobot of blue and red where G1 Starscream's would be.
Although, I kind of like having unique chassis to make your own. I appreciate that they did both. I am very much looking forward to WFC II.