The first thing I would do is set up a folder structure to save your jobs into ie a convenient folder on the network where you will keep the maj files. I keep mine in a folder named "x:\CAMduct Drawings" for example. Within that I have subfolders for all the different contracts so they can be found or new jobs added easily. CAMduct by default saves them to a folder like:
C:/Users/Public/Documents/Autodesk/Fabrication <version>/Imperial Content/<version>/PROJECTS/ , but you can specify a different location.
To do that you need to run "Edit configuration" from the start menu > Autodesk > and then look in your CAMduct version it should be in there. From there set a location (under "Project") of your choice so that when you open or do a new job it will follow that path.
To create a new job you can:
•From the Utility Bar, click the New Job button.
•From the File menu, click File New Job.
•From the Job Browser dialog, click the New Job button.
Clicking the New Job button from the Utility Bar displays the Job Wizard dialog. On the Job Wizard dialog, to create a new job, choose one of the following options on the New Job tab:
•Takeoff New Job: Select "Takeoff New Job" then click Next to display the Enter Job Information dialog. This creates a New Job using the Global database, creating a .MAJ file type.
Enter your required items and save.
I recommend reading through the "Fabrication Help Files", click "Help" on the top menu bar and click "Contents" you will find further information in there.
Hope this gets you started....