Assuming you have all the parts, the gun is pretty simple, operating like most blowback striker fired guns.
Starting cocked, pulling the trigger pulls down the sear, releasing the firing pin. The firing pin goes forward, fires the cartridge. The pressure forces the cartridge case to the rear, blowing the slide back and operating the disconnect mechanism. The tail on the striker rides over the sear. When the recoil spring reasserts itself, it pushes the slide forward, chambering another round and leaving the striker caught by the sear, ready to fire again.
Jim