Once signed into Zoom, you find the Audio and Video under "Settings". The "gear" icon in the upper right.
Once you click on the "settings" you will see this screen and you select which setting you need to modify.
Click on "Video" and you will see this screen:
Under camera, you see all the options for your web cam. If you have an external one it will show up here with the integrated webcam.
Click on "Audio" and you will see this screen with all of your audio settings. Under this drop down is where you will select your speakers:
Under this drop down is where you will select your microphone: