Steps to use Simple Mail Merge:
1. Create a draft email in Gmail. Use variables for keywords you want to be replaced dynamically. Use {{ variable }} to distinguish a variable.
2. (Optional) Create a Google Doc that you want to include as an attachment with the email. The attachment is sent as a PDF in the mail. Use variables for keywords you want to be replaced dynamically. Use {{ variable }} to distinguish a variable.
3. Create the Data sheet in Google sheets with columns same as the variable names. Configure the Simple Mail merge add and send email to your clients.