The manual helps a lot in using jumpgates.
Letting the A/I cruise you through is one way,
if you insist on doing it manually,
Must make sure it is select as the current nav target.
Approach at any speed, dead ahead, while it is still selected.
If it is not the current nav target, you can pass right by and never enter it.
How do you get to Carnegie Hall?
Practice, practice, practice.