Wondering how to fast travel in Doom Eternal? You will unlock fast travel for each level a little before you complete that level. Fast traveling can get you to different points in a level you've already visited.

How to Fast Travel in Doom Eternal

If you're not looking for it, you might miss when you get the ability to fast travel. When you're near the end of a level, you'll get an indicator that fast travel has been unlocked. You can then select the region, and then points within the region will be quickly accessible.

— DOOM (@DOOM) March 20, 2020

Like most games, you can't fast travel when enemies are nearby. Strangely, you lose the fast travel capabilities of a level when you replay it. If you're on a second or third run, say, you'll have to unlock it again. This is most likely to prevent players from skipping ahead in difficult portions of a second run. Once you complete the level, you won't be able to go back into it unless you replay it.