If I understand your question right…..
You don’t!
The 1611 was created to convert the old MCL system to the (then) newer ML system.
The BL3500 is a dedicated link speaker that needs a master (audio or video) to be used.
If setup right, you can draw on the sources from e.g. an audiomaster/the sources there (radio/cd……).
You control the BL3500 with the remote – have a look here:
https://www.beoworld.org/prod_details.asp?pid=373
MM
