The advice to date, while all good, concentrates on PP (post-processing) software. Depending on how many pictures you take, and how you file them on your HD, presuming that’s what you will be doing, I think it best not to delay too long using software that also will allow you to easily and efficiently catalog and, more importantly, find and retrieve images you want to work on or view.
LightRoom is a popular program that does this, while also being a more-than-adequate program for PP. It is excellent for letting you experiment and make all kinds of changes to your images without actually changing the original image. This will help you easily learn and visualize how various PP actions affect your images, always allowing you to go back to the original. Huh? In simple terms, in LR you are viewing a thumbnail of the original image, and edits you make are software instructions that do not change the original pixels (image). They do appear as changes in the thumbnail image you are viewing.