In the Main Menu, select Setup | Data Paths to bring up the following window:

Paths refer to the locations of folders. There are three paths, and the explanations above each text box should be all the information you need when entering the path. When you are done, click OK. If you do not enter a valid path, you may not be allowed to continue.
If you are using Pract-Eze Dental on multiple computers, you will need to share the C:\Pract-EzeDentalData folder. Right click on Pract-EzeDentalData and select Sharing and Security...

Make sure both boxes are checked as shown above. Then, the path the the main window above would be \\server\Pract-EzeDentalData\, assuming the name of your server is 'server'.