If you don't see/have that option from 'Stardock Forums' you can login to Joe User and you 'should' be able to from there.
[hard for me to be certain as I have that access everywhere].
Yup, JoeUser is the only place you can do it now, you could once upon a time do it from impulse_driven, maybe you still can, but i would imagine not.
You may have to write one blog (thread) from joeuser to get it to work (that was the process on impulse_driven) but since i post from joeuser as well, i couldn't be sure.
<edit> Jafo, i think only Ambassador or higher forum rank enabled you to have more control, IIRC, and only if the forum ranks are still in effect, and then only on the native SD site you gained said rank from. I believe Mumblefratz had more user control on GC2 due to higher rank, for instance. <edit>