I made a circuit for connecting 2 motors to this h bridge, now My question i need help with is how would i connect 4 motors to this h bridge?(if that is possible or would i need 2 h bridges ?) thanks. I am using at atmega328 chip

 

You would need a 2nd SN754410 to connect two more motors.
All the outputs are already used on the one shown in your schematic.