|"how do i check my psu"|
If you're 100% sure the PSU is connected properly, the switch on the back of the PSU is ON, & you get nothing (no lights, no fans, etc) when you press the power button, it's pretty likely the PSU is bad. There is no easy way to test it other than to swap it out for a known good PSU. A Dell PSU may work, but you provided no info about the Dell so it's impossible to say for sure.
And just an observation, you could use more RAM.