Registering applications with Asterisk

Hi
I have an external application to register with Asterisk, such as the convert module available at redice.krisk.org/. For the installation, the C file has to be compiled as make AST_HEADER=/path_to_asterisk_header

How do I find this header in my installation? The default header is not valid for my installtion.

Thanks for the help.

Harshat

Looking how it is done in other asterisk applications which are already registered in your installation