Help I'm lost on this hack

. Sorry to sound dumb but I just bought a vB licence today, I got my color scheme all done so I decicded to start to do some hacks and this is nothing like ubb lol, well actualy the hacking part but anywho I get to this step:
Changes to
postbit template (1)
postbit template
Step 1 of 1 FIND:
$post[editedby]
AFTER that ADD
<br>$post[editedreason]
Now where are these template or postbit template files

. This is probely a stupid question b/c I bet it's right under my nose but I never did a vB hack yet and this would be my first one so I'm just wondering where the heck this is. All help apprecaited, thanks!