Okay, I'm a noobie on this board. How do I do this?
Couldn't be simpler, LMouse. You see that icon that looks like a pad and pen at the top of your post? Click on that and you'll get back into your post. You can edit the body of the post, the header, etc from there.
To add a blue arrow, just click on the circle next to this option on the 'message icon' list at the top of your post, after you hit the edit icon.
ETA: I see after posting this that you've either figured it out already, or an Admin or Mod has done the deed for you. But I'll leave this here anyway, in case any other newbies need the info.
LabRat
