You can ask for microphone permission or let Snapcall ask it at call start (ask if you plane to receive call)
To integrate a outgoing call in your app in few lines in your Activity
var bid = "khjdshkfhskXZB"
Snapcall.getSnapcall().launchCall(bidId: Bid, parameter: null)
The bidId String is the identifier you created in the Snapcall back office . It can be the same as your web call.