If your smartphone supports ANT+: Go to Settings > Devices > Connect ANT+ belt. The app will then search for the belt.
If your smartphone does not support ANT+: If you have Android version 3.0 and higher AND your device has USB Host capabilities then you can use an ANT+ USB stick together with a USB OTG (OnTheGo) cable. The Nexus 7 tablet, the Samsung Galaxy S2, S3, S4 and many other high-end newest devices have USB Host capabilities. You need to install the ANT Radio Service App, ANT+ Plugins App and the ANT USB Service App.
If you are not sure whether your smartphone has USB Host capabilities, you can down load an app in Google Play to check this.
When you are up and running, you go to Settings in your app > Devices > Connect ANT+ belt.