W1D3 done!

I'm excited to move on to week 2.
BernerDoc, I've used CalorieKing (back when it was free/cheap) and SparkPeople, and those sites have multiple entries for running and walking, based on speed. They'll calculate the calories burned based on your age/weight. I'm guessing the ones you mentioned are the same. If you don't know your speed, you'll need to measure or estimate that.
I just log the running and walking as two separate entries. Alternating them might actually burn more calories (by keeping your heart rate up for a while during the walking sections) but underestimating the calories you burn is generally better than overestimating

(within reason). So for example, week 2 workouts have 6 running segments, 90 seconds each, so that's 9 minutes of running to log. And that means that with warm-up and cool-down, you'll do at least 21 minutes of walking.