The arms are in a group layer.
The group layer contains a vector layer called sleeves and a switch layer of different hands.
Is the group layer a bone layer? If not there are no bones to bind to. If yes you could only bind the arm vectors to any bones if the parent of the arm is a bone layer. The arm layer must be inside the bone layer. To bind points you select the bone and the points while on the vector layer. Then select the binding tool. The bone binding tool should be available if the vector layer is "inside" or a child of a bone layer with bones.
(Edit: this is the bind points tool in the bone section of the tool palette:
)
You don't need to bind points to a bone if you are using region binding. The binding method of the bone layer makes no difference if you are binding points. Points bound to a bone are "locked" to the bone. There is no "flexible" binding when using point/bone binding. It is a direct "one to one" relationship. Pick a point or points, select one bone, bind the points.
The switch layer can ONLY be bound to a bone in the parent layer (the same parent as the arm vector). You can't bind points in a switch to the parent bone layer because it is another level up in the hierarchy. You can put bones in a switch layer but I'm not sure you need this... although I can't be sure from the description.
Imagine there are 3 bones in the arm layer, bicep, forearm, hand that are over the vectors of the arm and over the hand switch layer and you are using region binding without any point binding (this is what I do anyway).
Bone layer (parent)
-----> Arm vector layer (influenced "automatically" by the bicep, forearm bones)
-----> Hand switch layer (bind layer to the hand bone)
Let's talk about one more thing. Putting the arm in it's own bone layer. I use to do this myself in the beginning
until I learned it was so much better to use bone offset and have my whole rig in one bone layer. You can read about this in the tutorials and help.
Think about the animation process, with each arm or limb in its own layer you will have to constantly switch layers to do any animation. It slows things down. It is just a suggestion.
I do however put hands in their own switch or bone layer bound to a hand bone in the main skeleton rig. I think of hands and fingers as "different". Generally I would do the larger motion acting, the broad stroke type of animation of the body then go back and do hand animation which is "smaller" and more detailed. Like when you sketch; you don't draw each finger when doing rough sketches. Later you go back and add those details.
I am rambling on again. Hope some of this was even close to the info you needed.
-vern