I agree Gimp or Photoshop can be totally cryptic but have been using Photoshop for decades - particularly for image manipulation and have come to an understanding with it.
There are some basic tutorials on line. It might be worth spending a bit of time learn, but that is all dependent on your need/desire/etc.
As Kat says there are a few on-line tools I've heard of that allow you to make covers -- I think there is even one in the Amazon Author area.
I suspect there are a number of tutorials about making book covers around as well...I just fly by the seat of my pants.
There are many artists around as well that will do the job for you for a full range of prices. Unfortunately I don't have links but I've seen them posted even here in the writers section.