Use the PROP tool (in the Tools menu) to set the x and y of the particles to the same value. Shift + right click to remove the topmost particle in a stack to check that you have layered successfully.
@Potbelly(View Post) The first one does not work This is invalid: "!set x CRMC QRTZ". It just sets x position to 0. But the !set x <id> <pos> will definitely work.
I would suggest using PROP instead of console anyway, since it is easier