An important part of Gimp is Layers. Layers act as panes of glass which have been painted on or have an image on them. From above they all look like they are one entity but if you remove the top sheet of glass, they will look different. This can be achieved by right clicking on the layers and selecting Add Alpha Channel. Images which are PNGs will already have alpha channel added. Right next to the layer is an eye, click on it to change whether the layer is visible or invisible.
The pencil, the brush and the rubber are the most well known Gimp tools. You can adjust their settings and the type of brush in section of the Tool Box called Tool Options.
The magic wand or the wizard wand is the fourth tool of all the tools and it has the ability to select everything that has a similar colour and then delete it. Once you are done with it, click outside the image (so the grey sections of the application) to get it rid off it.
The text tool is also easy to recognise. It gives you the ability to make font bold, itatlic and underlined. You can also change font size and the spacing between letters.
The last tool is the dodge and burn tool. This tool can change the darkness or the brightness. Dodge will make it lighter and Burn will make it darker. The settings can be adjusted in Tool Options in the Tool Box
Once you have finished editing your image, go to files and then click export. Click Save or Save as to save it as a Gimp file. This means you will be able to sae it later. It will be saved as a xcf file.
If you've lost the tool box or layers window, don't fret. Press ctrl b for the tool box and ctrl l for the layers window.