When you get off US 93 at the Nevada Exit 2, turn right at the stop sign.
The road back to the dam has some great views. Before the new bridge, all traffic both ways had to travel across this road.
There is a security check point that you must go through to get into the dam area.
The parking area for the Hoover Dam Bridge is just ahead. Note the walkway that zig-zags back and forth to the top. It's a bit of a walk, but well worth the effort.