The minimum recommended watts for gtx 1050 and 1050ti is 300watts, I would recommend going for gtx1050ti if you were to buy a gpu.
But even though is has the minimum watts there is no guarantee it would run it, you would need to know how much amps it delivers, do you know the exact model? Since your pc is prebuilt they have cheaped out on the ram, motherboard and psu, using the parts that can only just run the cpu and gpu they are paired with. I would recommend upgrading motherboard, ram, psu as well as gpu. What cpu do you have and what is your budget?