It's in the top-right side of the Gmail page. A drop-down menu will appear. This is the shield-shaped icon in the drop-down menu. Doing so opens your Google Account page. It's on the left side of the page. You'll find this option on the right side of the page, above the section where you enabled 2-Step Verification. Type in the password that you use to log into your Gmail account. It's below the password text field. This grey text box is on the left side of the page. Clicking it prompts a drop-down menu. It's at the bottom of the drop-down menu. A text field will appear. Type Outlook (or something similar) into the text box. It's a blue button on the right side of the page. Doing so will create a 12-letter code on the right side of the page; you can use this code to sign into Outlook. Click and drag your mouse cursor across the whole code on the yellow background, then press Ctrl+C (Windows) or Command+C (Mac) to copy the code. You can also right-click the selected code and click Copy.

Summary:
Click the "Google Apps" icon again. Click My Account. Click Sign-in and security. Scroll down and click App passwords. Enter your account password when prompted. Click NEXT. Click Select app. Click Other (Custom name). Enter a name. Click GENERATE. Copy your app password.