To choose the same device for both microphone and speaker use:
Step 1: Select the Additional Settings icon in the bottom left of portal to open a pop-up.
Step 2: Click on the Microphone icon.
Step 3: Select the devices from the options listed. (This is pulled from windows)
To choose a microphone and speaker individually
Step 1: Click on the Settings icon on the left.
Step 2: Select the Audio Device option.
Step 3: Select the devices from the dropdowns of the microphone and speaker.