Adding to a directory using terminal

[Strychnine]

Hello forum, I'm a new mac user having a hard time with something that could be so simple to someone with experience, thought I'd give this a shot.

I would like to add -console to an existing application which is located on my desktop. /vampire.app -console

How do I locate this with the terminal so I can make the changes?

This is for a game called Vampire the Masquerade: Bloodlines

I am not running an emulator or mounting disk images. Thanks!