Hi Peter, I understand that you want to change your default search engine on Firefox for iOS.

To do so, simply follow these steps:

1. Enter Firefox, then click the menu button in the bottom right corner.
2. Select "Settings" (it should be directly above the menu button when you press it).
3. Under "General", select "Search".
4. If you wish to add your own search engine here, select "Add Search Engine" under "Alternative Search Engines".
5. Under "Default Search Engine", click the first option.
6. Now, select the new search engine.

I hope this helped! If it did, please mark this reply as the solution so that others can resolve their own problems in the future.

Thank you and have a great day!

For Firefox on iOS (for iPhone/iPad) https://support.mozilla.org/en-US/kb/change-your-default-search-engine-firefox-ios https://support.mozilla.org/en-US/kb/enable-or-disable-search-engines-firefox-ios

However if you are actually referring to (desktop) Firefox on macOS as it is not clear if you are referring to on iPhone/iPad or on a Mac https://support.mozilla.org/en-US/kb/add-or-remove-search-engine-firefox https://support.mozilla.org/en-US/kb/change-your-default-search-settings-firefox