combining cubes

I was modeling my arm. I made the upper and lower arm together. I finished what I made and on the same layer, I created the hand. I tried to combine them by editing them, but it will only let me edit one at a time. I cannot link the verticals together. I know I have done it before but I do not know what I have to do.

Thank you.

i think what you are saying is that you have 2 separate objects and you want to combine them into one object. select both in object mode and hit ctrl+J to join meshes. now when you hit Tab to enter edit mode both objects will be editable

Hey thanks alot!