Create a new template by opening your DealMachine mobile app or logging in with your computer to https://web.dealmachineapp.com
Click the menu button in the top left (mobile only)
Click create new template. Click Save.
If you want this template to be the default for new deals, click the menu button in the top left (mobile only), click Settings, click Sending Options, Set My Default Template.
If you want to apply this template to existing deals, click into a deal, click the "options" button within the Mailing Addresses section. Then select the mail template.