my-hacks – WPGRINS

This is the first time I’m using hacks and I’m not clear about somethings.

I want to use Alex’s WpGrins for clickable smilies.
I know you have to make a “my-hacks.php” file and stick the code in there without spaces and in the admin area have it checked (legacy).

I need to upload the wpgrins.php file somewhere.. but I don’t think it’s under /wp-content/plugins directory because when I try puting it there, I don’t see it appear there. I want to make a folder called “hacks” or something but I don’t know where I put this file?

Can anyone help me out here? =)
Really appreciate you help guys!