🚀 go-pugleaf

Did you make shapes, or just draw lines to make your logo? In the latter case you cannot fill a line. If it is a curve, you can fill the area enclosed by the line and the start and end points, but this is seldom what you need.

However, if you have shapes, select with either pointer (black selects all, white selects only a part of the shape, but the background will fill all in both cases). Now, select the color picker near the bottom of the toolbox (two overlapping squares). Make the upper one come to the front. Double click it to select different colors. Just picking it with something selected should fill that something. (The other sqaure -- lower right -- is for stroke, or outlining a shape).

Have fun.