Step 3: Add the atoms

Now we will add the Na and Cl atoms:

Make sure periodic display is turned off
Select the Sodium (Na) element tool from the periodic system that appears when you
 click the '>' button

After this the toolbar should look like:

Click once in the drawing area, near the origin
Click once on the created atom to stop bonding

As you can see the atom is not exactly in the origin. This can be fixed if you wish:

Use the 'Set Origin' command from the 'Edit' menu

To add the Cl atom you can proceed the same way. You do not need to use the element tool this time, because there is already a chlorine tool predefined in the toolbar.

Click on the Cl-tool in the toolbar
Click once somewhere in the unit cell
Click on the new Cl atom to stop bonding

Next you should edit the Cl coordinates and change the Cl color:

Change the Cl coordinates to be (2.75,2.75,2.75) in the 'Coordinates' panel
Click and hold on a the Cl atom
In the pop-up menu, use the 'Define Cl Color' command and choose a new green Cl color
Turn on periodic display (in the 'View' menu)

Now your system looks like: