Summarize:

Click or double-click the Microsoft Edge app icon, which resembles a dark-blue app with a white "e" on it. In some cases, Edge will resemble a dark-blue "e". It's in the upper-right corner of the browser window. This option is at the bottom of the drop-down menu. It's near the bottom of the Settings menu. This option is about halfway down the screen. Click a search engine that you want to use as your default. This button is near the bottom of the window. Doing so sets your selected search engine as the Microsoft Edge default for any future searches performed in the address bar.
Open Microsoft Edge. Click . Click Settings. Scroll down and click View advanced settings. Scroll down and click Change search engine. Select a search engine. Click Set as default.