Optional: Talk to Aldo in the Tenshodo, inside the Neptune Spire Inn in Lower Jeuno.
Bring your Delkfutt Keys, obtained during your nation's 3-3 rank mission to avoid walking up the tower.
If you have the Upper Delkfutt Tower Home Point #1, take it, it'll take you right to the elevator to the Stellar Fulcrum and get right to the fight. If you don't, be sure to register it after you make the climb.
Once inside Delkfutt's Tower, if you have a Delkfutt Key, make a left at the first fork and go to (E-8). Then go to (H-8) and search for a ???.