Article: It's in the All Apps area of the Start menu in Windows, and in the Applications folder on a Mac. If you're not already signed in to your Google account, sign in now. Your spreadsheet will contain a list of the recipients for your mass email. Here's how:  Row 1 should be the column headers, e.g. FirstName, LastName, Email, etc. Don't include spaces or special characters in these headers. Input the data for the people you're emailing. Make sure there's an email address on each line. Click Untitled spreadsheet at the top-left corner of the screen and type a name for the spreadsheet (e.g. Mass Mail). Click anywhere else on the sheet to save your changes. This is a mass email plugin for Gmail that allows you to send up to 50 free emails a day. There are upgrade options if you need to send more than that. It's the blue button near the center of the page. A pop-up message will appear. This installs the plugin and then redirects you to your Gmail account (and a pop-up message). An account screen will appear. A confirmation message will appear. If you don't see the account you want to send the mail from, click Use another account, then sign in as directed. This allows the plugin to access your email and spreadsheets. You'll be redirected to your Gmail inbox.

What is a summary?
Open Google Chrome on your PC or Mac. Go to https://sheets.google.com. Click + to create a new spreadsheet. Add the email addresses to the spreadsheet. Go to https://www.gmass.co. Scroll down and click ADD GMASS TO GMAIL. Click Add extension. Click Connect Gmass Now!. Click your Gmail account. Click ALLOW.