You wont see the grant mission dialogue box in the preview mode, only when you actually accept the mission in game through the remote contact system. As far as selecting the location where it starts, there should be a box that looks like this in your story section:
You can select the map and NPC/location you want the person to go to to start the mission. So far I've been setting it to sector space and using the local systems around Sol for convenience.
One thing that you might like is not setting it all until the very end. You can hit play from the story tab and almost instantly start the mission. You wouldn't have to travel to Andoria again and again.