Good first day, hewmon. Those are some good baselines to start working from. Out of curiosity, what did the app have you do the first day?
BTW, it's water under the bridge now, but once you reached those work sets, you were to do two more sets at that weight for a total of three sets, as described in the book—"Then do two more sets at the current weight, for a total of three sets across with the heaviest weight. And that is your first squat workout."—so your squats and would have been 135x3x5 and your press 85x3x5 for your workout. Your deadlift was good at single workset of 135x5.
re: practicing at home - don't. You'll get plenty at the gym 3x/week. Plus, us over-50s don't need the extra volume, even if it's light weight, and even this light weight will disrupt your recovery. It doesn't make sense now, but it will once your squat and deadlift get above 300lbs. Use that time to read the book(s) and watch the videos.
Your practice will come during your warmup sets for the next few weeks (and thereafter). For these next few weeks, keep doing x5 warmup sets like you did today, which means that you'll be doing 30-40 practice reps per workout (90-120 reps/week), which is plenty of practice. During that time, treat every single warmup rep as if it's a textbook work rep and that's your practice. In a few weeks, you'll want to start tapering those warmup sets down to x2's and x1's. The Grey Book has a section called, simply enough, "Warm-up" in the Training Program Basics chapter (pg 76 in the physical book). And while that book does a good job of explaining it, The Barbell Prescription (BBRx) does a great job over a couple of pages (pp 174-6), complete with examples. And not that I'm a great example to follow, I list my warmups and worksets over in my training log that may help illustrate what I'm saying.
As far as figuring out warmups once it gets heavier, I like the process that SSC Phil Meggers lays out here, since I'd rather not do too much thinking about what plates to put on the bar. That's the process that you'll see laid out in my training logs.
Enjoy feeling that work sink in over the next few days. It will slowly fade away as you get more consistent.
Keep at it!