Haha there's nothing wrong with paint, but there are things out there better suited to the task. As Sil said just keep experimenting as there's no one way of doing things and you'll soon understand how your camera responds. When you say that your images are 'RAW' are you saying that they're actually RAW files or just an unprocessed JPEG/TIFF?
I only ask because GIMP doesn't handle RAW images so you'll need a plugin called UFRAW to process them. If you're not interested in GIMP or don't like plugins then another free alternative is RawTherapee.
Here are the links for each.
UFRAW
http://ufraw.sourceforge.net/Install.html
GIMP
https://www.gimp.org/downloads/
RawTherapee
http://rawtherapee.com/downloads.
Happy imaging.