Stuck at the Settlements and unsure where to go

I did all the settlement quests and now I’m trying to go back to Helios City. The problem is, it won’t let me fly and I have no idea where to go to get out of Settlement Oscar. I went into the desert, didn’t see any way to go.

use the pikataxi guy if u have the emolga taxi if not u just go south until u are at the settlement north of the desert then west then south

Thanks. I took a break from the game and forgot where everything was. I kept going and found the settlement with the train.