Open Gmail
Click the gear icon
Select See all settings
Go to the Accounts and Import tab
Under Check mail from other accounts, click Add a mail account
Enter your office email address
Click Next
Choose Import emails from my other account
Click Next
Enter your office email password
Enter the POP server details from your office email provider
Set the port if required
Select the desired options for incoming mail
Click Add Account
If prompted, confirm the verification code sent to your office email
To send mail from Gmail using your office address, go to Accounts and Import
Under Send mail as, click Add another email address
Enter your name and office email address
Click Next Step
Enter the SMTP server details from your office email provider
Enter the username and password for your office email
Click Add Account
Confirm the verification email sent to your office inbox
Refresh Gmail and check that your office email is linked