The edge(s) helpfile states that in order "To choose an edge for which you qualify, "discuss guildmastername 'edgename'"." When I attempted it, the following happened however;

discuss guildmaster 'multi-word edgename'
You cannot discuss that with your guildmaster!

When I later on made a new attempt yet with the " symbol rather than ', as seen here...

discuss guildmaster "multi-word edgename"

...the edge was succesfully added to my character. Take note that I haven't yet attempted to choose edges the names of which consist of only a single word.

Any edge that has a ' in it, needs to be surrounded by " for it to work properly.

So long, and thanks for all the fish!