Open GIMP and then open an Image in GIMP
Next press CTRL+L together to open up the Layer Panel or click on DIALOGS->LAYERS to open the Layer Panel
In the Layer Panel, right click on the Layer you want to make transparent, and select ADD ALPHA CHANNEL
Then you need to select witch color you need to make transparent on your image. There are two methods how to access this function, Press CTRL+O together on the keyboard or click SELECT->BY COLOR, and then you select the color on the image with the pointer of the mouse that you need to make transparent. Click on it and it should make a selection.
Once you are happy with the selection you may press DELETE or click on EDIT->CLEAR and now the selection on the image should be transparent.
NB – REMEMBER TO SAVE THE FILE AS A “GIF” FILE!!!!! If you skip this and save it as a JPG it wont be transparent