Joining is easy, from the tower click on the "map" button on the clipboard. On the left hand side are 2 buttons. Viewer and Editor. To join a mission that someone has up just click viewer, select the mission at the top (can be many) select the flight you'd like to fly. Click on the Accept button at the top. This will launch you in the correct plane, with the right loadout at the right field.
Even if your in a tower halfway across the map.
Editing, well Ripsnort or Hazed are better at that than I am.
