I guess I left that out in my original post. I do have remote agents installed on these servers, but because I cannot see them in my browse list, I cannot choose them directly in the Remote Selections area under Microsoft Windows Network grouping.
This is the reason I tried adding them as a User-defined Selection, using the IP address of those machines, but when I choose them in this area, I do not have the Database options available for backup, only disk partitions and shares.