How to use DFRobots IR Break Beam Sensor (SEN0503) with a micro:bit?

Hello everyone

Just to mention right at the beginning: I don't understand a lot about electronics. I work with primary school kids and we use micro:bit microcomputers. 
The students have a project where they want to detect with a sensor if a table tennis sized ball moves through a gate of 20cm to 10cm dimension. I thought using an IR break beam sensor would do the job fine. But as much as I try - I can't make the sensor pick up any signal. How would I have to connect the IR-sender and IR-sensor to the micro:bit to make it work? And how would the code would have to look like? I've tried for many hours but it doesn't work. Any kind of advice would be greatly appreciated!

Beda