Click the gear icon in the upper-right corner and select “Settings”.
Go to the “Accounts and Import” tab.
Click on “Import mail and contacts”.
A new window will pop up. Enter your Outlook email address and click “Continue”.
Enter your Outlook email password and select the options for how you want to import the mail (e.g. import mail from the last 30 days, import all mail, etc.).
Click “Start Import”.
Gmail will begin importing your mail from Outlook. Depending on how much mail you have, this process may take some time.
Once the import is complete, you will receive a confirmation message.
You can now access your Outlook mail in your Gmail account.