From their README

This is an Alfred workflow that enables you to create a new task based on the selected mail message when using Mac OS X Mail.


After you install the extension you will be able to launch Alfred and type "mt" then type the task subject you would like such as: "mt Follow up on this email"

You can also add a due date to the task by adding "d: --date string--" to the task subject for example:

"mt Follup up on this email d:today" or "mt Follup up on this email d:next friday"

The date format follows Todoist date format found here: Date and time insertion

You will need to get your Todoist API token and place it within the applescript embedded within the workflow.

Additionally this workflow has a dependency on the JSON Helper app. You can download this from: Mac App Store - JSON Helper for AppleScript