You can also refer to this video guide
Or you can refer to the following steps-
Subscribe to a plan to enable the Email services in your account. HelpDoc
Add your domain to the MSG91 account by which your emails will be sent. HelpDoc
Next, you are required to verify the domain by adding the TXT and MX records to your domain hosting provider. HelpDoc
Once the domain is verified, you will have to create a template of the content you wish to send in the MSG91 panel. HelpDoc
Once the email template is created and approved, you can use it to send emails in the following ways-
1. Campaign (Multi-channel where you can add other services like SMS, Whatsapp, and Voice also)- HelpDoc [Recommended]
2. Email API (If you have a specific use-case where you want to use the dedicated Email API only and not use any other channels)- API Doc
3. Google Spreadsheet Plugin- HelpDoc