At the top of the hill, you'll land in a parking lot on the west side of the Golden Gate Bridge. As you approach the bridge, follow signs for bike and pedestrian walkways. You'll descend stairs to go under the bridge and toward the vista point on the other side.
Once at the north view point, you can peruse the memorials (to sailors, Coast Guard, Merchant Marines) -- and enjoy a spectacular view of the Golden Gate Bridge and San Francisco, looking south.
At this point, you can return down to Fort Baker, or continue your walk onto the bridge, using the pedestrian walkway on the east side.
More photos and information about the bridge: Guide to the Golden Gate Bridge