The first lesson does two things. It answers the question almost everyone brings to a singing course, and it takes a measurement.
The question is whether you can learn this at all. The short version from the guide below: for most people, yes. True tone-deafness (congenital amusia) is rare, and singing is a learnable skill. Research on inaccurate singers points mostly at the link between hearing a pitch and reproducing it, and that link improves with practice. The longer version, with the caveats and the research, is in the full guide linked at the end of this lesson. Read it if the doubt is what has kept you from starting.
The measurement is more important than the pep talk. Before you change anything about how you sing, sing a simple five-note scale and let the app score it. That score is your baseline. It will probably be lower than you would like, and that is fine. Every lesson from here on gives you a way to compare against it.
What to notice
The exercise is a five-note scale up and back down with a different vowel on each note: mee, may, mah, moh, moo, and back. With Demo on (the default) the piano plays the pattern once first; then it plays along with you, an octave above, while you sing. Do not aim for beautiful. Aim for on time and on pitch.
Pay attention to two things. First, whether you tend to land under the note or over it. Beginners often drift flat as the keys climb above where the voice sits comfortably, and the per-note results after each key will show you which way you lean. Second, which vowel felt easiest. "Mee" is bright and narrow, "mah" is open, the others sit between. Knowing which one your voice likes tells you something about where you are starting from.
The starting key is chosen from your voice part. If you skipped that choice, the app assumes alto. Change it in the exercise settings if the scale sits too high or too low.
What done means
Sing through the exercise once in Standard mode and log the session. That is the whole assignment. If the score is under fifty percent, sing it once more, and then stop. Repeating a baseline ten times turns it into practice, and you want a clean before picture.
Then decide whether to add the five-note scale to your routine. It is a reasonable first pick, because it is short and it works on the thing every later lesson depends on: matching a pitch you just heard.