Open Gmail in your browser
Click the gear icon and select See all settings
Go to the Advanced tab
Enable Templates
Click Save Changes
Compose a new email
Type the content you want to save as a template
Click the three-dot menu in the compose window
Select Templates
Click Save draft as template
Select Save as new template
Enter a template name
Click Save
To use the template, start a new email
Click the three-dot menu in the compose window
Select Templates
Choose the saved template
Edit and send the email if needed