In the mesh panel, under vertex groups, you can assign elements to a group using the weight in the slider. If you go to the materials panel, you can select all faces with a mat by clicking the “select” button. Then just go over vertex groups, select your head group, set weight to 1, and hit “assign”. Also, if the earrings are a separate object you can just parent or constrain them to the head bone, no need to skin them.