Before moving forward with this, please ensure you have first followed the steps outlined here.
To edit role acceptance notifications for an organisation, you need to set the notification scope to "role_successful_tenure" and the topic to "accept role".
The "Template Key" is the role which these templates will apply against.
If you like you can set a blanket notification template for a broad range of roles, eg all team official roles, or you can set the notification to only be relevant to a very specific role, such as a cross country chief marshal.
This allows you to be flexible with your templates and have unique notifications for each role.
In this example, we want to update the notification for all swimming event official roles, so we will set the template key to "event-officials-swimming". 
The "Attribute" dropdown refers the section of the notification we want to edit. There are three options here, the email_body, the email_subject and the email_attachment. We will update the email body in this example.
The above screenshot is an example of what you could change the role acceptance email_body to be, but the content is static and not very personable. To further customise your notification templates, you can make use of variables.