I'm not clear what you are trying to say. The fill is a normal object property like anything else and by default Flash will create filled objects and automatically close open paths. Well, whatever. Ask in the Flash forum.
Let's say you open Flash Creative Cloud. On layer one you make an arrow with the "pen" tool. Now let's fill it with whatever color you like. Make sure your last step in the process connects with your starting point (ie: No gaps in image outline. Fill bucket does not work with unconnected outlines). Wondering if in Flash CC if another layer is needed to do a fill color with "pen" tool.
O.k. then....after hours of this concern being on my shoulders, I finally tackled the solution. Firstly, grab your "pen tool" & create your image, go to your selection tool, then click in your images fill area (you should see a blue box outline around your entire image now), go to bucket & give it a color of your choice!