armature animation problem

I’m trying to learn how to use the armature animation sstem, but everytime I enter then exit edit mode, the vertecies of the object I’m trying to “change” disappear and only a wireframe of the oject is left, so I can’t assign vertecies to a group. Anyone know hat I’m doing wrong?

You MUST be in EDIT MODE to assign vertices to a group!!
Enter edit mode, make a new group or choose an existant one, select
the desired vertexs and press the assign button.
Keep Blending
António