I don't have my tcl script for my project handy right now but here is a simple way to figure out what the correct syntax is. open up the project in quartus. Add a file or two in the GUI. then write out the tcl script. The GUI version can do this. Now you can open the generated tcl script and search for the file that you added. The syntax for adding files may then be replicated. This is also a handy thing to do to dfine I/O pins, types, and logic lock regions. Generate a sample of each of the pertinent things that you want in the GUI and then write out te TCL script.
Once you have the syntax it is much easier to just use a text editor to add more items.