Bustoville

No worries Bustoville, you didn't make any mistake. We all need to start somewhere.
Thanks for the file. There's several ways to approach this. Here's one easy to follow
- select the Pen Tool and draw a shape covering the inner area of the hexagon. To do this simply click on each "corner" of the hexagon with the tool until you complete the shape - see the clip below (no sound) then move this shape below the Outer_Logo layer. Fill it with the colour you want.
 

 
- to insert an image/icon inside the shape, draw or import/place (menu File ▸ Place) the image/icon you want to use into the document and move it over the shape you just created. You may need to scale the image/logo to fit the inner area of the hexagon - to do this select the Move Tool, click over the image to select it and drag one of the corner handles to scale it proportionally.

I do not completely understand what you mean about adding a fancy border color as a child layer. Is there some reason you can't just set the stroke color of the shape to the desired color independently of its fill color?
 
I don't understand your last question at all. Are you talking about a pixel selection saved as a raster file or what?

Hi Bustoville,
Welcome to Affinity Forums
Seems you are working with pixel layers rather than vector objects (take a look at the label after the layer's name in the Layers panel) and using Affinity Photo. Can you confirm this please?
It would much easier for us to help if you could also attach the file so we can see what you are trying to do (you can delete all layers non-related with the issue if you want). Thanks.