The first step is creating a user (profile). You can have as many profiles as you need - one profile for each child. Click on the 'plus' button to create it.
Enter his/her name and select a picture. Picture can be taken either with the built-in camera, or it can be selected from existing pictures in the image library. You can move the picture and zoom it as you need.
You can edit existing users after selecting your profile and by tapping on the top navigation bar.
Then click on the 'Settings' button (gear in head icon) and adjust the difficulty of the generated equations. You can also completely switch off operations that are not needed, and modify the ranges of the generated variables and possible results.
You can check the generated equations by clicking on the button below the range settings.
The 'Maximum available time' setting on the profile page sets a time limit for each answer. The minimum allowed time is 5 seconds, the maximum is 100 seconds. Answers have to be entered within the time frame otherwise they are evaluated as incorrect.