There are two user accounts needed to make the ETL’s work.
The SSRS user is created at the server level. Once created, they can be added to the databases.
The account should have reader, writer, admin and owner memberships to the two databases.
The ETL connection are kept in the Connection Manager and Parameters. Update the placeholder connection to valid credentials.
If any of these are not needed, delete them from the ETL or disable to steps.
Several data connection in the Clarity ETL are
csv files. There is a pdf setup guide
Extracts and Exports Instruction Sheet.pdf included in that download.
It is possible that not all tables that Atlas uses are exported to your Clarity database. You may need to enable additional tables.
The Staging database can be created using the creation script.