Here are some of the most basic techniques involved in using graphics programs and software. Obviously each program will work different ly but there are some things which are general to most graphics programs e.g. selections, layers, colourising, cropping etc.
I do not profess to be either a graphical designer or a graphical artist but I have been using various graphics software for over 15 years so feel able to talk about the basics at least.
I am a firm believer that good graphical design skills take education (even self education) and practice. There are no end of sites which will help you with this if you wish or better still, think about taking a course. Remember even the best software wont make a graphic designer out of someone who wasn’t before. In the same way that buying a Steinway wont make you a pianist, you would still need the lessons and the practice.