As users, gain and lose reputation, they are associated with a moniker that describes their current level. These levels are modifiable by navigating to User Reputations->User Reputation Manager.
<<insert image of reputation manager>>
In the above example, we have all of the levels that users on this forum can achieve. For example, a user with a reputation of 55 would have the level of will become famous soon enough. A user with a reputation of -5 would have a level of has a little shameless behaviour in the past. Since the lowest level in this example is -99999, any user with a reputation lower than this would use the default undefined level that is set in the reputation section of the vBulletin Options.
From this screen you can choose to edit a level description, change a level minimum or remove a level. If you wanted to change the minimum level of has a reputation beyond repute from 2000 to 3000 you would enter 3000 in the input field where 2000 is currently and press Update.
If you wished to change the text of has a reputation beyond repute, you would press the Edit link.
<<insert image of reputation editor>>
From this screen you can also change the minimum level as you can from the previous screen. Enter the new level text in the Description field but take care as you can not use HTML in this field. Press Update when finished.