The easiest way to perform a stereo bounce is to choose File > Bounce (or use the Toolbar Bounce button or key command). This will open the Bounce dialog for outputs 1-2 of your primary audio device. It is recommended that you use the first output pair for main playback duties.
Note: If you are using other output channel strips for primary playback duties, click the Bounce button on these channels.
You can set the file format, bit depth, and sample rate of the bounce file in the Bounce dialog. Detailed information on all bounce parameters is found in the Logic Pro User Manual.