1. Select the net the copper it on, and then right click and select 'add via'. If the copper isn't on a net I don't believe you can add vias. Others may have more insight.
2. Draw a 'copper shape' on your solder mask layer.
You can do both in numbers of different ways.
For item 1 - select net in question - RMB 9right mouse button) - select Add Via command and add desired vias inside geometry representing this Copper.
For item 2 - if the Associated Copper is part of Decal, in Define CAM Documents select Solder Mask for this layer, select Edit, select Layers, select Layer 1 or Solder Mask layer (depends where this copper is), select in Items on Primary - Pins with Associated Copper check Pads, Open Copper and Filled Copper or just what is applicable.
If it is just a piece of Copper on Layer 1, create same piece of Copper on layer Solder Mask Top. For that you can use standard Windows Copy - Paste command. After pasting new copper piece, change Properties for the new Copper shape to be on correct Solder mask Layer.
Copper Opennings.jpg 211.8 KB
Thanks for your good and helpful answers.