Hold/Transfer calls API functionally

Hello,

I come around Polycom API as short project to integration with ERP , I success to make post Dial call using API, But still can't not understand how to make transfer or hold for call using the API commands.

for holdcall also transfer call, Polycom API documentations which is very helpful but still need more explanations and samples.

{ "data": { "Ref": "<CALL_REFERENCE>" }} 

can you please explain how I know what/where to found the value of CALL_REFRANCE .

also this the same for transfer call

{ "data": { "Ref": "<CALL_REFERENCE>", “TransferDest”: “<NUMBER>” }}

Thanks in advance.