I'm relatively new to cortex command, and I see some mystical "activities" pop up in posts that supposedly should work in skirmish. Could someone please tell me where activities are found, how do I make them wirk, and how to cook them properly?

Thanks...

As you're relatively new, and I'm not that kind of person, I won't explode with rage.

Always, always use search on the wiki and here on the forum before you ask a question, very likely it has been answered before.
In this instance, what you want is on the wiki, in the form of this activities page.