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The recommended method for giving another person access to a shared email account is by "delegating" access to the user. When a delegate accesses the shared email account messages, they do not need to enter the password for the shared account. To add delegates to an account, follow the steps below:
- Log into the shared Gmail account and select Settings then See all settings

- Select Accounts
- Under Grant Access to your account select Add another account
- Enter the email address of the person you want to add.
- Click Next Step then Send email to grant access
The person you added will receive an email asking them to click a link to confirm. The link expires after 1 week. If they do not click the link to accept the delegation, they will not have access to the delegated account.
Note: It may take up to 24 hours for delegation permissions to take effect.
You can also select the option for how the sending address appears:
Sender information
Select the one that works best for your requirements.
Once your delegate has confirmed the link, they will see the account listed when they click on their Google Account icon in Gmail. They will need to click on the Delegated account in the list of accounts and a new tab will open for the delegated mailbox so they can read, reply, manage or compose new messages for the delegated account.

For additional information about Delegate Access, visit: https://support.google.com/mail/answer/138350?hl=en