You need to read the doc material for the new MQTT (v2) Binding to see some examples:
i) MQTT - Bindings | openHAB
ii) MQTT Arrives in the Modern openHAB 2.x Architecture | openHAB
iii) Migrating MQTT1 items to MQTT2.4 items
iv) multiple posts within the community forum with generic examples of MQTT v2 configurations (text based and/or PaperUI based)
v) The specifics of your broadlink-MQTT-Bridge setup will have to be figured out by yourself. If you get stuck, post what you have tried and ask for help.
vi) After you have successfully configured your OH2 system to work with MQTTv2 configs for this Bridge, type up a tutorial so can share the knowledge 
