i don't under stand pls explane more in wich template to edite and .......
It's difficult to know which template you need to edit since you aren't stating where in your forums you want the userid to show - my guess is that it's the postbit or postbit_legacy template in which you should add $userinfo[userid] wherever you want the member's userid to appear within the template.
you can get to the postbit template in AdminCP>Style&Templates>StyleManager> then click expand templates and search for the template, copy and paste the html into dreamweaver or notepad, and then...