Question Removing panel on HP Pavilion 550-132ng?

You will need to remove the 3 clips facing the camera simultaneously(or one at a time) then pry away from the fascia of the chassis towards the right(of the pic).

Your prebuilt should be coming with a 180W PSU, I'd advise against dropping that card in that case unless you've gotten a higher wattage, reliably built PSU, preferably a 550W unit. Due to the size of the case, you should be in good order if you got an SFX PSU.