Hello ; Solder mask layer and bottom layer are two separated layers while making your design you can handle each one of them aside, if you create a copper area in the bottom side of your design than all copper pads connected to the same net of the copper area will be connected automatically to the bottom side of your board and no need to handle anything manually :) For example, you are using the GND net to create the bottom copper area then all parts connected to GND will have them pads connected to GND automatically once you produce the GND copper area. About the solder mask layer, no need to touch it because the connection will be generated in the copper layer automatically. Please move this post topic to "PCB Layout" Thank you.

"Please move this post topic to "PCB Layout"" You can do this by changing the Category. You do not need to repost your topic. To clarify: You do not need to do anything to the Solder Mask because the copper pads on PCB Footprints have their own apertures in  the Solder Mask. These apertures are preserved no matter whether they are connected by tracks or surrounded by copper created by Copper Areas or by Solid Regions set to Solid. As advised elsewhere, why no make a simple dummy project, take it all the way from creating the Schematic, Converting to PCB, up to generating and checking the Gerber files and then you will be familiar with the tools and you will see from checking the Gerber files, the answers to this and many other questions.

thank you both!!!