If you want to use the GMX Search as the default search engine in your browser, first
you have to add it first as an additional search engine in Mozilla Firefox. Follow these
steps:
Click on the menu icon in the top right corner of your
browser window.
Click on Options.
Click on Search.
Scroll down to the list of One-Click Search Engines.
Click on Find more search engines.
Search for "GMX Search" and click on the matching search result.
Click on Add to Firefox.
A confirmation window pops up.
In the confirmation pop-up click on Add.
You will be asked if you wish to set GMX Search as the default search engine.
Click on Yes.
GMX Search is added as an additional search engine in Mozilla
Firefox.