To access the Configuration, click your profile icon in the top right of the Dubb Dashboard, then select the option that says "Your Settings"
The left navigation will change and you will see a tab that says "Team", Click "Team" and then you will see a tab that says "Configuration".
Please note for personal Gmail accounts the limit is 100 emails sent per user per day. For corporate accounts, the limit is 300 emails sent per user per day. Learn more here.
Here is a video on how to configure your Gmail to Dubb.