You should see this screen once you’ve successfully opened the link.
Step 2: Press on the play button to open the app. You should see the screen below.
Step 3: Click on the first tile, the one that says “Atom” to access the “Build an Atom” screen.
Step 4: This exercise is designed to help you get familiar with the atoms in the Period table. You can start building atoms by adding protons, neutrons and electrons.
For example, if you added one proton and one electron, a neutral hydrogen atom was built.