To select the mic, speaker, and camera you want Teams to use for calls and meetings, click your profile picture or symbol on the top right hand side of Teams, then Settings > Devices.
Under Audio devices, pick the speaker and mic you want Teams to use by default.
Under Camera, select the camera you want Teams to use, and see a preview of that camera's video.
If you have multiple devices connected to your computer, you can set one as your secondary ringer, which means it'll ring when a call comes in. Answer incoming calls on any device—not just the ones that ring.