I made a quick little reply under the FSP thread about this, decided I'd make a little more in-depth guide with pictures due to boredom! So let's get to it, shall we? :3

First off, if you see this:

Press CTRL+ALT+D.

Once that is painstakingly accomplished you should now see this:


Good, we're getting somewhere. Now, with utmost care, place your cursor over the shiny new tab and click it. CAREFUL, don't want to smudge any pixels here. New drop-down menu appears:


Now gliiiiide your cursor ever-so-gently down over the Show Debug Settings selection, caress it with a soft click. With that out of the way a wild debug box appears. This, my friends, is the fabled Debug Settings:


All silliness left aside, read the tooltip. It explains stuff that nobody should have to. Now that we're here let's get to the real reasoning behind this guide.

----- CLIENT VERSION -----
Once you have your debug box open, in the search type in "SpecifiedVersion". Your options should be now limited down to 4 options as shown:

**THESE ARE NOT IN ORDER HERE IN THE MENU** -- Correct order is: Maj.Min.Patch.Build --

Let's say you want to spoof as the current version of Firestorm which is: 5.0.1.52150
You want to do the following adjustments:

SpecifiedVersionMaj: 5
SpecifiedVersionMin: 0
SpecifiedVersionPatch: 1
SpecifedVersionBuild: 52150

Doing it this way allows you to get over that pesky 3 digit limit on build under the provided spoof option.

----- MAC & ID0 -----
Now with the previous information that you have been given the following images should be sufficient enough to help you in want you're attempting: