Callisto requires read permissions on the Configuration Manager database, this is granted using SQL Management Studio. There are a few ways to achieve this, our recommendation is to grant a Callisto User group datareader rights, it may be that you already have a group you can use for this purpose.
Assigning Permissions to a Callisto Users group
Open SQL Management Studio and connect to the required SQL instance. Execute the following script replacing the domain and database names.
CREATE LOGIN [domain\Callisto Users] FROM WINDOWS;
CREATE USER [domain\Callisto Users];
ALTER ROLE db_datareader ADD MEMBER [domain\Callisto Users]