There are many existing H-bridge designs for discrete components. These days the main switches are always MOSFETs. Google "MOSFET H-Bridge circuit", choose one that you like the look of and try to understand how that works. If you have trouble ask again.
You have much more chance of getting help with a specific circuit than with very general questions, particularly since none of us knows what you already know. You started by saying you know little about electricity and a bit later you were claiming to understand how transistors and MOSFETs work...those two statements can't both be true.
Steve