Subscriptions not set up correctly, need help

When I go to subscribe to a report I get
"Subscriptions cannot be created because the credentials used to run the report are not stored, or if a linked report, the link is no longer valid"
Everywhere I've looked says I have to edit the data source in the properties of the report but everything I've tried fails. The report runs fine using a shared data source and "Windows integrated security" but subscriptions do not work. I've tried "Credentials stored securely in the report server" with my own log in (full admin rights on both the VM and SQL server) and still can't get it to work. Any help would be appreciated. Thanks in advance!

I believe you need to setup and execution account for SSRS - that will be a domain account that has limited permissions that will be used to execute the reports.

That account will also need to be granted the necessary permissions in the databases where you are getting the data for the reports.

The other option you have is to create a SQL account on the server/database with the appropriate permissions and use that account in your data source.

Okay, I have a domain user id that I can give the necessary permissions to but I just don't know where and how.

You can use either your local SSRS Configuration Manager (if it is the same version) - or login to the server and use the SSRS configuration manager there...

There is a page where you setup and define the execution account.