Connect an audio interface to your computer. An audio interface converts the audio signal from your microphone or instrument cable into data for processing in Soundbooth. The method of connection varies according to the make and model of your sound card, but it typically calls for either a single USB or Firewire cable. Connect the relevant cable to the port on your computer.
Open Soundbooth. Double-click the desktop icon, or click "Start," then "Programs" and select it from there. If using a Mac, use the desktop icon or open Soundbooth from the "Applications" folder.
Click "Edit," "Preferences" and "Audio Hardware," then select your audio interface from the drop-down menu. This assigns it as the default hardware device.
Click "File" and select "New Audio." A small box with a number will be in the dialog box. This indicates the number of tracks of the specified type to be opened. The default number is "1." Delete "1" and enter "2." This opens up a pair of channels with the same settings. When prompted to select between "Mono" and "Stereo," select "Mono." Typically, it would be preferable to record in stereo, but since you're recording two sounds anyway, keep it mono for clarity. Two new audio tracks will open.
Connect each microphone to an XLR cable; the female end of the cable goes into the microphone. Connect the male end of each cable to an "XLR In" or "Mic In" socket on the front of the audio interface.
Name the new audio files. Click the text box on the audio channel strip to edit the default name from "Audio 1" to something more specific. Use a name that reflects the function of the microphone -- for example, "Vocal close" or "Vocal ambient."
Audition each microphone. Sing or play into the microphone and observe the gain meter in the Soundbooth interface. If it is flashing red, the signal is too strong and will distort when recording. Correct this by dragging the channel "Gain" dial down on the Soundbooth channel strip. Repeat for the other channel.
Set each channel to "Record Ready" by clicking the red "R" icon on the left of the channel strip.
Click the "Record" button in the navigation section of the Soundbooth interface. As Soundbooth records, a sound wave graphic will appear in both channels. The sound waves will differ according to the function of each microphone. For example, if one microphone is farther away, its sound wave peaks will be smaller in comparison to the closer microphone.