Dublin - without wishing to sound a smart**** - "you" don't.
It's a moderator 'power'. What I used to do (in the days when I din't know HOW to post a link) was just point people in the direction of the thread that you would like to be answered - with a phrase like "Please don't respond here - post replies in the thread on **** forum"
Or write to amod and ask them to lock one for you - or "sticky" one if it ought to stay near the top for a while.