The clue here, I believe is in the part of the error message that says "...you must create the estate owner account first..."
That would indicate to me that you have not first created an avatar account, first. If your running OpenSi9m in Grid Mode, you need to do that in the ROBUST console like so:
create user
Then enter the avatar first and last name - and other details when prompted
After creating a user, you should then be able to create Estates and/or join regions (sims) to them
Hope this helps, & good luck with your OpenSimming KingofTheVoid
P.S. Hi Amethyst - long time no see x