Right below the window named "Your Reply" is the window named "Tagline". Just type a tagline in that window. When you post your reply it will become your tagline until you change it.
Right below the window named "Your Reply" is the window named "Tagline". Just type a tagline in that window. When you post your reply it will become your tagline until you change it.
Aha !
BTW, it might be time to change your tagline! ;^)