how do I get google to be my default search engine on my home page

My Mozilla crashed and for about a week I have been running it in safe mode. Today I tried it and it is coming up but my default search engine does not show up like it used to. Mozilla Firefox is my home page and in the middle where there is supposed to be a seach engine name which is google in my case and there is nothing there except the search box. Some how in the manage search engine at first in the popup nothing was listed. Then somehow It managed to make Firefox Help as a search engine and today somehow google showed up but it won't let me make it the default search engine. The manage search engine popup window will not let any of the buttons become available to work. I really don't want to reinstall it if I don't have to because I have some book marks I don't want to lose. I changed my Firefox back to the 16 version by restore system. It brought back to 16 version but that's it.