To grant Gmail access to someone else follow these steps
Go to Gmail Settings (top right gear icon) > click "See all settings"
Select the “Accounts” tab
Under “Grant access to your account” click “Add another account” (You’ll have to verify your sign in”
Enter their email address and select “Next step”
It will prompt you to review your permissions, click “Send email to grant access”
This will cause them to receive an email invitation to accept access. Once accepted, they can view your emails by clicking their profile and selecting your account. This won’t cause them to have access to your personal information, they will only be able to view and send emails on your behalf!