I have an Android phone. Can I use Google Fit with World Walking?

Yes. 

World Walking can connect to Google Fit and bank all steps recorded on the Google Fit app. Google Fit is an app (download link -> https://play.google.com/store/apps/details?id=com.google.android.apps.fitness) which automatically tracks all the physical activity you do that Google is able to record. So if you go for a walk, the GPS data on your phone can be used by Google Fit to store the route and the total distance you walked. On top of this, some higher end Android devices come with a built in pedometer, and Google Fit can use this and other sensors to gather even more accurate information about the activity you've done.

To start banking steps from Google Fit, go to the Settings page on our app and click Connect to Google Fit. You'll be prompted to connect your Google account at this point.

From then on, whenever you open the World Walking app, it will check how many new steps you’ve accrued, and if it’s more than a few hundred, the app will add these steps to your bank. You’ll receive a popup telling you when steps have been successfully banked. Bear in mind that this accounts for all steps you take when you have your phone, so if you use the GPS tracker you may end up banking the same steps more than once.