See also video to the right.
When opening an app you may get a popup asking you to grant access to your home folder (whatever username you are logged on with). Click confirm.
Navigate to the folder on your Mac where you would like to save your files, and also want to be able to open files from that particular folder.
Then Click Open
Then Click Done
To Open a file from a location on the Mac or save to a location on the Mac, Choose File, Open, or File Save as, then expand This PC. When you see a list of available drives, you will see drives on (name of Mac). Choose that and then choose the folder you initially selected to save the file on your Mac.