Select Print File from the File menu to print your piece. You will see the standard Windows Print dialog.
Make sure you have set up your print the way you want it (correct printer, pages, number of copies, etc.) and press OK to print. For more detailed information on the Print dialog see your Windows User's Guide.
You can change the staff size for your printout by changing Print Scaling in the Print Setup dialog, available from the File menu. This changes the aspect ratio of the music by stretching in the y direction while keeping the x direction constant.