Find the membership you'd like to customize an email for.
On the right next to the title of the membership click on the three dot icon to open secondary menu.
Choose 'Email templates'.
You'll be redirected to the email templates editing view.
Make sure 'Sign Up Email' tab is open.
This tab lets you customize your message subject:
And your message body:
Make note you're allowed to use shortcodes - special system variables, which will be replaced with actual values when an email is sent. Shortcodes must be wrapped in double curly brackets in order to be detected by Member App platform. A list of available shortcodes is added below the message body editing text area for your convenience.
Once you've customized your message template click 'Save' to permanently store your changes.