Here y go, step by step
1. Click on the Settings icon in the top right, and select ‘Manage add-ons’.
2. In the ‘Manage Add-ons’ window, select ‘Search Providers’ in the left pane. You should now see Bing as the default search engine in the list of search providers in the right pane.
3. Click on ‘Find more search providers’ link in the bottom left.
4. This will open up Microsoft’s Add-ons page for search providers, where you can browse and select any of the search add-ons, including Google, Wikipedia, eBay.com, Amazon, Yahoo!, ESPN, Facebook Search, Hulu, Lyrics, Photobucket, and so on.
5. You should be able to find Google in the first page itself. Click on ‘Add to Internet Explorer’.
6. When asked ‘Do you want to add this search provider?’, select the check box ‘Make this my default search provider’, and then click ‘Add’. By default Search Suggestions is enabled. If you want to turn off search suggestions then clear the check box ‘Use search suggestions from this provider’.
7. That’s it. Now close the Manage Add-ons dialog and re open it via Settings –> Manage Add-Ons. You should now be able to see Google listed. Remove Bing if you want to have only Google. Select the check box ‘Prevent programs from suggesting changes to my default search provider’