From BitWise DocuWiki
The master account is the account that we create for you as the first account in your Professional Network. You will use the master account to administer your Network, such as creating the other accounts that you will need in your organization. Other accounts can be also be given administrative privileges at your discretion.
There is no reason you can't use the master account for regular use, so most people choose whatever name they would like for their own BitWise name. For example, if your name is Ellen McDill, you might choose an account name like emcdill, ellenmcdill, mcdill, etc.
Please note that account names must be 15 or fewer characters.