-get an image

-If your image has a white background or a single colored background to get rid of it go to "filters">"colors">"alpha colors" and press okay

-If your background color isn't white select the bar select the background with a dropper tool from the image then press okay and then press okay again.

There are 2 ways to select a new layer:

-Select the new layer button at the bottom of the layers tab

-or near the top left select the arrow then "layer menu" > then "new layer"

-name your layer "white back">then select "white" then okay

-grab the line-art layer and put it in front of "white back" layer

-By doing all of this you have now prepared your line-art for coloring. Instead of your image being colored over its under making it a lot easier.