To use the weld tool everything has to be on the same layer, on the rights side of the screen you should only see one color swatch, if more than one select all then right and left click on the black color swatch at the bottom of the screen, you may need to enable this feature by going to View > Pallettes > and selecting Show Job Pallette.
For your spinner, break the part if there are any objects on the inside, if you have an inside and outside border make a path on these two objects, select your border then select the part you want to weld, click on your Weld Tools then select Basic Weld.