Navigate to the Chrome Web Store
This can be accomplished by opening the “Apps” menu to the left of the bookmarks bar, or by searching “Chrome Web Store” in the omnibar.
Search for an app using the search bar or select “Extensions” to browse:
When you find the extension you want, click the blue “Add to Chrome” button:
The extension will show up as a small icon to the right of your omnibar. In most cases you will click on this icon to activate the extension.