When you reach this point there is a supply room on the right that can be opened by using the controls next to it. Head through the large round door to get to the exterior of the ship.

The panels above will slide open. Head up the ramp and onto the exterior of the ship.

There are three exposed electrical units that you must activate. They are located towards the right-hand side of the saucer.

After the three units have been activated, head to the top center of the saucer. Warning: There is a glitch in the next quest. Hit "Save" now so you can hopefully overcome the glitch if it happens to you. The circle in the center will now be lit up. Step into the middle. Just like when you were first abducted, you'll float up and into the upper part of the ship.

The white light will subside and you'll find yourself standing inside the upper part of the ship. It is NOT safe to remove the spacesuit yet, though you will get the quest complete notification.