Streamlabs OBS for Android and iOS is a free streaming app that is great for testing things out before you make the jump to a paid software.
Disclaimer: We're aware that this app may be buggy and sound loss in a live stream is unfortunately, not uncommon. Use at your own discretion. (If you're looking for a more solid option, and are willing to pay for an app, please consider OBS Camera, which you can download from the Apple store. If you are an Android user, consider using CameraFi.) If you move forward with Streamlabs, here's how you can try to troubleshoot audio issues on your end - https://support.streamlabs.com/hc/en-us/articles/360012057413-Streamlabs-Mobile-App-FAQ
Install the app, and once you launch it you'll see the login options:
Choose Other Platforms and you'll be prompted for an RTMP URL and Stream Key:
These of course are found in Uscreen and to make it easy on yourself, copy paste them and email them to yourself so you can copy easily from your email on your phone.