first you need the temple,

after you buy the temple you can gently lower the stickman into the castle and a light will shine down and after a short time he will be converted. at this time a blue stickman will show up on the top portion of the screen.

once you have the archery range you can click the flag in the archers tower and it will add the stickman to that tower. they fire automatically so you don't have to do anything to make them shoot the arrows.