take your PSU and fit it to a friends computer. see if it works.
that will be the easiest test you can do. testing your motherboard isnt really possible as you need a Known Good same socket CPU, known good RAM & PSU also
easier just to wack your psu into another PC to test it.
If that does not work, pls post you system specs and i can look further into it.
psu is most likely the culprit. just to make sure you check everything tho, try a different power cable if you have one (ensuring it's completely plugged in) or a different power outlet. also, make sure the psu switch is set to ON LOL