Hi

I am not sure what you mean. Microsoft Edge is a different web browser, you cannot "add" it to Mozilla Firefox for Android.

Are you trying to use Microsoft Bing in Firefox for Android?

If so, follow this guide:

https://support.mozilla.org/en-US/kb/manage-my-default-search-engines-firefox-android#w_add-a-search-engine

and set the search string to:

https://www.bing.com/search?q=%s

I beg to differ, have already added Yahoo and Brave Search engines

I am sorry, I do not know what you mean.

To use as the "Default search engine" for Firefox

Do you know how to open a xpi file?

The guidance I provided previously will help you to add Microsoft Bing as a search engine in Firefox for Android.

To open a .xpi file you would be best using a desktop computer and treating the .xpi as a .zip archive to open it.

I beg to differ, have already added Yahoo and Brave Search engines

To use as the "Default search engine" for Firefox

bing.com. google.com, duckduckgo.com, yahoo.com are examples of search engines.

Microsoft Edge https://en.wikipedia.org/wiki/Microsoft_Edge is a web browser so you cannot add a web browser to another web browser.

The Brave web browser and the Brave search engine are separate things.