The GSW-H1000 watch will refresh the heart rate reading every 10mins if you're not doing an activity.
If you're doing an activity you will need to go into the activity app screen and select your desired activity. Once the desired activity has started the watch will record the relevant information ie distance, speed as well as heart rate in real-time.
When you're not doing an activity the heart rate can only be shown on the digital watch face. To swap the watch face hold down the screen with your finger for about 2 seconds and scroll through the options available.