ok

i'm the same but at gimp I'm a master of photo shop even though I hardly ever go onto the program.

there are tutorials or if your not in the mood to watch it just make a new layer go on to paint (make sure the colour is black) look at the top of where the settings are you will a scale saying opacity then click on the scale to 50% and draw in the area.

if that does't work it might be best to go onto you-tube as a second option.

no-one is a noob it just takes time to understand things. ^_^