Confused to Patch Diff File

[Anggi Lesmana]

Dear Ubuntuers,

I would like to ask one thing. How to install/patch
http://machekku.uaznia.net/xmpp/psi/patches/attic-qt3/psi-machekku-smart_reply_and_forward-0.5.diff

So far I couldn't patched the smart replay & forward feature. Could you
explain to me? What is the tools which can be patch it to my PSI-plus?
Actually, I'm using Ubuntu Desktop 10.04

Very thanks for your support.