Adding DuckDuckGo as a search engine in the default BlackBerry 10 browser

1. Open the default BlackBerry 10 browser.
2. Visit the DuckDuckGo homepage in the browser.
   
3. Tap the menu icon (three dots) on the bottom right.
4. Tap Add search.
   
5. Tap Add.
   

Adding DuckDuckGo as the default search engine in the BlackBerry 10 browser

1. Open the default BlackBerry 10 browser.
2. Start to type in the search bar.
   
3. Tap the dropdown on the upper right.
   
4. Select the DuckDuckGo entry.

Install the official DuckDuckGo app (BlackBerry 10)

Follow the instructions here. You can get the DuckDuckGo app .apk file for installing here.