1) Go to Gmail settings
2) Go to the Accounts tab, and down to the “Grant access to your account” tab. There will be a blue “Add another account” link to click. Click it.
3) You will be prompted to add the email address of the account you want access to be given to.
4) And to confirm that you typed in the proper address
5) An email granting access will be sent to the email address you specified
6) If you decide later that you no longer want that person to have access to your account, go back to the accounts tab under settings, to the same place where you granted them access, but this time, to the right of the email you have granted access to click the blue “delete” button, and that account will no longer be able to access your email
7) You will confirm that you want to revoke access
8) Here is an example of what the email giving access to your account looks like
9) Once they click the link to access the request, they will receive confirmation
10) To access the account, you can just click up in the top right corner, where your gmail photo is, and you will have a (delegated) account. If this doesn’t show up after 30 minutes, click the “accept request” link in the email again, and then the account should appear in the bubble.
SOURCE MATERIAL:
https://support.google.com/mail/answer/138350?hl=en
VIDEO TUTORIAL:
https://www.youtube.com/watch?v=tVfrzsMe_UY