You can print a single-track part by setting the Score button in the Score Editor to Single Track mode and then selecting the Print File menu item from the File menu. This is recommended.
To print a group of two or more tracks select Print Part from the File menu. These tracks need not be contiguous. The Parts dialog appears after selecting Print Part.
Select the tracks that you want to print by dragging over contiguous tracks and CTRL clicking non-contiguous tracks, or to erase selected tracks. Of course if you just want to print one track, just click on that track. When you have selected the tracks you want to print out, click on OK. It will take a second or two to set up the tracks selected for printing, and then the Windows Print dialog will appear. 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.