Choose what to practice

First of all you'll need to tell the app what's the extension of your voice. As a rough indication, female voices can go as low as F3 and as high as C6, while male voices are in the range E2 - C5. If in doubt, you can start with C3-C4 if you're female, or C2-C3 if you're male and then refine the extension's upper and lower boundaries as you proceed with the exercises. All the exercises that the app generates for you will include only notes within your vocal range, which is why it's important that you are as precise as possible.

As far as the exercises, you can choose:

The tonality (or set of tonalities) chosen from the 12 major tonalities and the 12 minor tonalities available

The type of exercise, with the options including: scales, arpeggios, and random notes.

and The intervals that you wish included in the exercises (this option only applies to the random type of exercise)

For example, you can choose to practice scales of D and G, or intervals of second major and third minor in the tonality of C.