I do it like this:

1) Enter the intro chords
2) Enter the chorus (remember that BIAB defines chorus as "everything between intro and end" = verse, chorus, bridge, ...
3) Enter the ending

4) Set the end to the end of your ending
5) Set chorus start / end and number of repeats

6) In Song/Additional Song Settings do all this:
a) Check "Tag Exists?"
b) Enter the bar# where your last chorus should end (the last chorus must not run until the end defined in step 2)
c) Enter the bar# where your ending starts into "Tag Begin at Bar#"
d) Enter the bar# where your songs ends
e) Uncheck "Generate 2-Bar Ending for This Song"