Using an NPN tranistor as a switch for two bipolar stepper motors
In the data sheet you can see the following extract: -



It shows inverters (highlighted in green by me) doing exactly the same as the transistors in your circuit. There are extra inverters also shown but these can be presumed to indicate that the control A and control B signal sources are from a logic device.


  My question is what do the wires control 1 and 2 lead to? is it just
  back to the GPIO pins of the microcontroller and i code for when the
  transistors turn on and off, or is there another piece of equipment in
  between?


They are fed from your GPIO pins and you code appropriately. Although the extract shows extra inverters, these are not needed and you can directly drive from your GPIO pins if they produce a logic 1 level in excess of 2.3 volts.


  what resistors and transistors to use?


I'd use inverters (74HCT types) and not transistors but if you are keen to use transistors virtually any common transistor will do. In fact I can't think of one that wouldn't work OK. The resistor values shown in your picture are appropriate.