This is the place where you configure a sheet you would like to process. Everything what you configure here add-on saves and automatically restores once you switch back to the sheet.
A source sheet is the sheet which is currently selected in the add-on. If you want to process a sheet in a spreadsheet you need to switch to that sheet first. You need to tell the add-on explicitly which sheet you would like to process. Add-on will try to restore entire configuration for that newly selected sheet if it was configured before. Add-on automatically switches to the active sheet when is opened.
This way, you can have a different sheet configuration for each sheet in a spreadsheet. By switching between sheets add-on loads different configurations.
Select a draft you would like to use as a template. The draft must contain at least one merge field. Add-on creates a copy of the draft for each row which is being processed and replaces merge fields with data from a sheet.
TIP: Take a look how to create your first merge draft.
Select a label which you would like to add to each created or sent draft. It is optional but strongly recommended. Once messages are labelled you can easily filter them out in your Gmail folders.
Configuring A Sheet
There are few things you have to always do in order to process a sheet: