1. Select block or range you wish to export (doing "select all" and then "transport -->locators to selection" -- shortcut "p" -- will set the range selection to span the entire project.
2. Choose "File -->Export --> Audio Mixdown...".
3. In the export dialogue these should be the default setting:
You can, of course, modify these dialog settings if you know that you want something specific. For example, you may wish to export an individual mono track by itself. Here you would choose "mono" instead of "stereo interleaved". Or you may be working in a higher sampling or bit rate and may wish to preserve this fidelity by exporting at the same high values.