I have several objects that all make up one big person. I want to rig this person but I can't because whenever I add a vertex group to weight paint, it only adds it to one of the objects. I don't understand how I'm supposed to rig several objects as one body (without merging it as one object, which I cannot do.)
Am I doing something wrong?? People act like weight painting is really simple but they always do it on one big mesh.
Edit: Also how do I attach a vertex group to a bone.
your question for "how do I attach a vertex group to a bone" is answered by how-to-assign-vertex-group-to-single-bone, although you can assign to more than one group in succession, I believe (and then perhaps need to adjust weights if >1 group). Here I took a sphere and parented it (Armature Envelope weights), which generally would parent it mostly to the right arm and spine area. I then put the sphere in edit mode, selected some vertices , created and assigned to a new "group1" (just I could select them later if needed), but ALSO assigned them to the automatically created group "hand.L" (left hand). As you can see when I posed the Armature to swing the Left arm upwards, my selected vertices of the sphere tracked with the left hand position. Here's my blend example: 
