[App_rpt-users] how to setup rpi3 based allstarlink node ,for a sip phone call radio ？

I have setup a rpi3 + DMK'S URI + BF-888S for a allstarlink node, but is not public of allstarlink , and I have config some sip account for a sip phone(with 1001) and my linphone app (with 1002), I can call each other with sip app and sip phone , but I want to call the radio from the sip phone (or app)，how to config the asterisk and app_rpt for it? Thanks a lot for help.