The following pertains to the "MS SQL Server Reporting Service (SSRS) Manager" section of Control Panel.
The "MS SQL Server Reporting Service Information" section contains the default username, root path and report server URL.
MS SQL Server Reporting Service is set up with a default username that cannot be changed or deleted. Up to 25 additional users can be added in the "SSRS Report Users" section. Usernames must be from 4 to 10 characters in length and can contain only lowercase, alpha-numeric characters.
Click "Edit" to change the password for a specific user. To change a username, first delete the user, then recreate it with the desired changes.