"issue linking is currently disabled" warning should link to some documentation

when I have no 'issue linking' turned on I'm shown a warning box right after creating issue. If I don't know what that's "issue linking" is I'm left with no clue where to dig (jira documentation? bamboo documentation? is it config in bamboo? or jira?). Would be cool to link to some CAC document (or even Jira documentation) that shows what is and how to turn on 'issue linking'