Done. Click on "external link" on the edit menu and insert address of this page (edit menu temporarily unavailable).
Or just type in the tags *[ Forum Topic] around the address:-
*[http://www.spaghetti-western.net/forum/index.php/topic,600.msg8738/topicseen.html#msg8738 Forum Topic]
If you want to put any feature on a wiki page and don't know how to, you could look for a page already with this feature, click on edit to see what tags have been used, then click on your back button (without actually editing that page)