Congrats on a good kit choice. My batch became ready for drinking last week and it’s very good. I’m going to apologize in advance for all the info and opinions I’m about to drop but you’ve selected a kit and yeast that do better with some intermediate skills not all first-timers have to deal with.
The nutrient pack feels like a ketchup pack inside the bigger pouch. I find it and center it on the edge of my kitchen counter. A moderate press with this method will usually pop it without the horror stories I’ve seen lately of some people popping the whole darn pouch. Yuck!
With a liquid yeast, either the Wyeast smack pack or a White Labs vial, it’s highly advised (required for the vial) to do a starter to build up the number of yeasties. This becomes more important with OGs above 1.055 or so.
A starter is just a mini-beer made with (generally) 1-2L of ~1.040 OG wort. You boil up a small batch of wort, pitch the yeast and let it ferment for a day or two. This can double or even triple the yeast count. See here (http://yeastcalc.com/) for a pitching calculator. When it’s done you can either dump the whole thing or put it in the fridge for a day or two to try and decant some of the unwanted beer off the top. I usually keep a pound of DME on hand for these.
All that being said, if you can’t find the activator you’ll probably be just fine dumping it into your fermenter after you’ve cooled the wort and added your top-up water. Try to get the wort in the 65F range or so. This being your first batch we’re going to tell you to relax, don’t worry and have a craft brew (since you don’t have any homebrews yet). There are many worse things than pitching a sub-optimal amount of yeast.