Open avast user interface' from the menu

...or double-click the desktop icon of installed avast! antivirus software to open the avast! user interface,

Click the 'ADDITIONAL PROTECTION' tab and from the unfolded submenu select 'WebRep'.

There you will see the list with the icons of supported Web browsers. Colored icons indicate Web Browsers present on your computer with the WebRep plugin installed, while gray icons indicate Web Browsers which are not present on your computer or have not the plugin installed. to uninstall the plugin click 'Uninstall' next to the colored icon of your Web browser.and go to the option chrome extensions

open the browser chrome extensions tab
Open the folder files and programs> AVAST Software> Avast> WebRep> Chrome and find the file
AswWebRepChrome.crx drag and drop the file to the chrome extensions tab to pop up a window and click ok to add. ready.
check enabled and activated.