example 1: NaCl crystal

The first thing that needs to be done is to select the builder. You do is by selecting the "coordinates" tab, and then select from the "Edit method" selector the "Builder" button

Now you are presented with a sort of form that allows you to build periodic structures.

It basically consists of three parts: a part where you define the original crystal lattice,  a part to define a surface, and a part to change the size of the unit cell. At the bottom is the button to generate the coordinates. Only the relevant parameters are enabled. For instance, because we are building a bulk system, all entries in the Surface frame are disabled.

To make the NaCl crystal, you should select as the bravais lattice "Sodium Chloride"

Next you should enter the two elements that comprise such crystals. Choose Na and Cl.

Enter the lattice constant, which is experimentally 5.64

Finally, push the "generate coordinates" button, and you are ready. You can switch back to the "Normal" Edit method to see the lattice vectors and atom coordinates that you could also have entered directly as explained in the previous tutorial.