EPM9320 development

I would like to extend and complete and existing hardware with EPM9320 circuit. The old design cannot be used with the current existing hardware. I am looking for a translating/developing program and downloading tools that will allow me to create a new design for the hardware.

The free program that can be downloaded from your website does not support this. (compiling) Can you please suggest another developing program (downloadable for free if possible) that would allow me to make the changes in my current hardware as mentioned above (EPM9320).

I appreciate your help in advance.