If you decide to import your contacts from Google Contacts, MailMerge will automatically list all your recipients in your spreadsheet. But if you want to add manually your contact list and other personalized information, here's the right way to do it.
You can either reuse an existing spreadsheet or create a new one. We'll start from a new Google Sheets:
On row 1, type the name of each column (called 'headers') for each information you need for your campaign.
We want to add the first & last names of our subscribers, their phone, location, and email addresses. We'll write these headers as following:
It is now time to fill your spreadsheet with all the information you need, row by row:
Once your spreadsheet is ready, you can now start your mail merge (after creating a simple draft email template in Gmail for your mail merge).
Click Add-ons > MailMerge > Start email campaign. MailMerge will automatically detect your contact column:
Input appropriate sender's name and select your simple draft email template in Gmail for your mail merge.
Once you're ready, simply hit the 'Send Emails' button to send your mail merge to your recipients: