NEW USER - overwhelmed by options - How do I...

[Ofnuts]

Taking it in the wrong order IMHO:

I would 1) get a path with whatever I have and 2) use the path to get a filled image.

To get the path, two ways:

Looks automatic but will be painful in the end

1. Select the background with fuzzy select
   
2. Select>To path
   
3. Edit the path to smooth the lines (pain point)
   

Looks hard but easier in the end

1. Create the path from scratch, using the initial drawing as a template (much cleaner path with fewer anchors)(*)
   

Note that the way selection works on a path, if an outline path intersects with itself the intersection is not selected. So in this drawing you have to make 4 paths, and create a complete selection by adding each to the selection. Another way is to avoid lines crossing each other, but to keep everything aligned to have to make lines intersect first.

So here is how it looks after 10 minutes:

   

The full XCF is attached

(*) No as hard as its looks, a rather efficient technique is to draw a polygonal path, putting anchors where the curvature changes ("inflexion points), then shift click between two such points to add an anchor and drag it to the drawing border.