How can I link the alien ship to the travel agency computer?

You can do that from within the alien ship.

Of course you will need to find the alien ship first.

Come back when you've located and entered the alien ship.

If you've entered the ship, you've met your host.

You will need to get past the alien leader before you can do anything else.

Come back after you've temporarily incapacitated the leader.

Now you can reach the LEVER behind her.

Pull the lever towards the planet to link the spaceship with the controls on the planet (that would be Earth).