Tutorial: Make the ORIGINAL (better) google your default search engine
If Firefox doesn't have the "ADD" button:
Step 1: Type about:config in your Firefox address bar and acknowledge the warning,
Step 2: Search for browser.urlbar.update2.engineAliasRefresh, set it to boolean, true
Here is the string to copy. Make sure to get the whole line!
https://www.google.com/search?q=%s&udm=14
00:00 - Intro
00:22 - Firefox
00:55 - Chrome
I disabled comments because they were all just fighting about whether or not you should be using google. Use whatever search engine you want - this is just a tutorial on how to do this, if you want to.