Okay so you have overlapping account structures in your active account structures - you need to review your active account structures and decide why you have >1 and the structure, if you have 1 remove the overlapping ranges of accounts.
Create and assign unique dimension set values and remove the optional flag - but those are pretty self explanatory from the message I hope.
Some background from you would be useful - how have you created this company and why are you creating it etc.