Assuming you would like a guide on how to change the search engine in Firefox:
6.
- Open up Firefox and in the top right corner, click on the three bars icon
- Once the drop-down menu appears, hover over “Options”
- In the new tab that opens up, under “Search” on the left side of the screen, click on “Manage Search Engines…”
- Find the search engine you want to use under “One-Click Search Engines”
- Click on the three dots icon next to it and select “Make Default”