ClarisWorks 2.0 comes with a VT320 Keys sample file which has shortcut buttons that provide a full function key set. You can modify this file for your use, or send the function key sequences manually with the following key sequences:
Press the Escape key, and then press a number key between 1 and 9, or the zero key for 10, hyphen for 11 and equal for 12. Press escape, then shift and a number key (or hyphen or equal) to generate function keys 13 through 24.
The same key sequences will work from ClarisWorks 1.0 Communications.