See image.
How does a dba go about granting access to the screen shown.
This is for a generic user using their AD credentials to access the ‘Reporting Services’ on a particular server. This is so that the generic user is able to create new ‘roles’ for SSRS. Currently only the administrator has access.

The image you showed belongs to connection to SQL Server which manage sql databases.
In most cases the reporting services installed on the SQL SERVER but it not mandatory. The reporting services server can be a dedicated one apart of the SQL Server.
The image you shown is the connection window to SQL SERVER
There Two option to perform a login:
Setup a login on SQL SERVER
The Reporting services has Report manager URL, which allows to manage report existing or add new reports ect..
In order to allow users to access the URL, you need to allow a specific user or a group to access the report server manager
Granting permission to the report manager
How to grant YOU access to a database
"Security"Tab"New Login""Search"button next to the"login name:"field"User Mapping"option"db_owner"After this you can create a data source with Yours user name
Does it what have you looked for?