[Asterisk-Users] Incoming call voice data

[Mag]

I am fairly new to asterisk. I have my DID set up with voicepulse.com. 
And when I call my DID I get an asterisk greeting. If I want to program 
my dialplan, as:

IF I press 5, record a 30 second message and save the file as message.foo


How can I do that?

Thanks