Lehi's image for the change required by his sons is interesting. He tells them to "awake" as though their current state comes through minds groggy with sleep that do not yet comprehend well the real world. For his sons, the world around them was the most real, for Lehi it was the spiritual realm. Lehis image is to awaken from the dreams of this world to the "reality" of the spiritual world.
One they are "awake" they may "shake off the chains with which ye are bound..." Shackles and chains would be a known image to the brothers, and they would know the difficulty of removing oneself from chains once they were applied. Nevertheless, were they to "awake" Lehi tells them that the removal of the chains is as simple as shaking them off. They become no longer a burden, and are easily removed if only they would turn to the Lord.
This awakening of the soul has other profound implications for the "slumbering" brothers. With the Lord's help, they arise from obscurity. It is not really clear how Lehi means this, but it is certain that in the least he refers to the state of their souls before God, and the effect upon their own person of the change that accompanies giving oneself to God.