The first thing you need to do is allow Gmail to accept connections from “less-secure Apps”:

• Log on to your Google account: https://myaccount.google.com
• Navigate to “Connected Apps & Sites” under Sign-in and Security
• Scroll down and turn “Allow less-secure apps” on

Then you have to enable IMAP for your email account

• Log on to your Gmail: https://gmail.com or https://mail.google.com
• Go to Settings, Forwarded and POP/IMAP
• Under IMAP Access, select “Enable IMAP” and then click Save Settings

Finally, configure Outlook manually using the following information:

• User information: Your name and your Gmail address
• Incoming server: imap.gmail.com
• Outgoing server: smtp.gmail.com
• Logon Information: Gmail address for the user name and your Gmail password
• Under More Settings, Outgoing Server tab, check “My outgoing server (SMTP) requires authentication, and select “Use same settings as my incoming mail server”
• Under the Advanced tab, use SSL and port 993 for the incoming server, and SSL port 465 (or 587) for the outgoing server