Administering FlashBB
FlashBB administration is done using the admin panel that come with your original forum.
For example, if you have FlashBB installed over phpBB, then you would use your normal phpBB administration panel, which is probably the "admin" subfolder of your phpBB root.
If you have vBulletin, then you would use your normal vBulletin administration panel, which is probably the "admincp" subfolder of your vBulletin root. This is also true of the user control panel in vBulletin - there is no Flash-based user control panel in FlashBB.
The reason for doing this is that the FlashBB skin is for end-users, not administrators or moderators. I.e., only you and your mods will actually see the HTML-based admin interface, not your regular forum users (with the exception of the user control panel in vbulletin). Also, the admin control panels in phpBB and vBulletin are very complex. Duplicating so much functionality in Flash would be quite difficult.