At the regular layout level, not within the Decal Editor, go to Setup > Pad Stacks, select the Via radio button and then click the button for Add Via. Name the via and set the parameters for its pad and drill size. I will have our documentation group review that help topic, it appears to be incorrect.
that is very easy to follow
You can ASCII out the vias from the older design and then ASCII the vias into the new design.