Substance Designer - Opacity Channel


I want to make a texture with some cutout tiling circles. But, I noticed, that a Base Material node, has no Opacity input.
How can I solve this?
I´ve built the network, but I don´t know if this is the correct way. It seems to be working, but I can´t find a way to export the texture:

Just for information: the nodes above seems to be correctly. To export the texture, just go to Tools > Export Outputs…