What are the variable in the settings.json when deploying mobile app on mLab?

Please I need help, like really big helps. I build my apk using

Meteor build command

App does not connect to connect to my mLab server. Should I set the server environment in the settings.json.

Even when I place the server information in a mup.js, it does not work. mup setup fail for timeout handshake.

Is there anyway to setup my server information in the settings.json?

Thank You So Much For Helping.