I’m struggling to add a related work to a recording…
This ought to be simple. Its a live recording of a Paul Simon song -
which is a live recording of
https://musicbrainz.org/recording/9d0e0aeb-034d-43d5-9d62-6b8028ae939b.
When I try to use the MBID (9d0e0aeb-034d-43d5-9d62-6b8028ae939b) in the relationship editor, and works as the relationship type it allows me to select ‘live’, but I can’t click ‘done’… What I am I missing please
You’ve made a basic mistake: Recording ≠ Work
This means you can’t select a recording for a relationship that requires a work. The solution is to connect both recordings to the same work (which has information about composition & lyrics).
Unfortunately there is no work for the song You’re the One by Paul Simon yet, but you can create it by typing in the title (instead of the MBID) and selecting Add new work. In the popup dialog you can now enter the information given in the booklet of the corresponding original album:
In this case that’s just the most basic information (assuming the song has English lyrics?):
More information can be found in the Wiki.
Thanks.
I need to study up on the data model some more…
However, Surprised that when someone added the album, it did not create the work… and that the UI did give me a good clue when I put the MBID in.
You might also want to give this tutorial video a look:
It covers using the Relationship Editor for adding/relating Works too. 
Edit: Possibly also give this introduction to the various MusicBrainz entities a watch:
