It's the icon that has a red, green, and yellow wheel, with a blue dot in the middle.  Tap the icon on your home screen or apps menu or Google folder open Chrome for Android. It's the icon in the upper-right corner.  This displays the menu to the right. It's near the bottom of the menu to the right. It's the third option under the blue "Advanced" header. It's near the bottom of the Site settings menu.

Summary:
Open Google Chrome . Tap ⋮. Tap Settings. Tap Site settings. Tap Ads.