Steps are simple: when it asks to pair with the device, double-click the middle button on the device and use “123456” as secret code. Repeat if it doesn’t work.
I was using the tbeam V1.1 board w/o screen
I somewhat cheated while I was testing by looking at the debug output from the device, as it is hard to tell whether the double-click was registered properly by the device - the button is so tiny and my fingers are so fat 
I needed to repeat it several times…