Open a Google Chrome window. Click the three dots stacked vertically (⋮) in Google Chrome's navigation bar, and click Settings. From the main menu of the Settings page, click Search engine, and then click Manage search engines and site search. Alternatively, go directly to chrome://settings/searchEngines. In the Site search section, click Add.

First, visit a search engine (or a website with a search feature). Chrome will automatically detect and add the search engine, if that site supports this feature. Next, right-click in Chrome's location bar and select "Edit Search Engines". Search engines from websites you've visited will appear in the "Other search engines" box.