Select your preferred search engine. If your favorites does not show up then you must close this menu and browse to that search engine.
Once you have done that just repeat the earlier steps to get back to this step.
After highlighting your search engine choice if you click/tap on Add as default it will make that your default search engine and you can close out the Settings menu.
If you click/tap Add then this search engine will be added to the earlier drop down menu as a choice along with any other search engines you add (including Bing which is on the list by default).