Trons are accessories that can improve your hero's performance. A hero can equip only two Trons at the same time.
To make a Tron, you should collect the parts. They can be collected in the Campaign mode (You can play the mode repeatedly to get them more).
In My Trons menu, you can see brief information of your Trons. Also, you can disassemble one to get some parts for other one.
When everything is set, you can select two blanks, next to the ability, to assign trons.