You use disk image files, not direct files on the storage.
You'll need a MS-DOS floppy or bootable ISO or CUE/IMG to boot from first. First you'll need an OS to boot(like MS-DOS or Windows). Then you'll need to install it on the hard disk image, just like a real PC.
UniPCemu doesn't support direct folder mounting like Dosbox.
It's using the same steps as a real PC, starting out with a blank hard disk(when created using the settings menu). You'll need some OS disk images for installing it and BIOS ROMs for the emulated hardware, which is mainly the motherboard and video adapter(except MDA/CGA cards). Then it's like starting out with a new computer with unformatted hard disk and unconfigured BIOS. So start it up, configure the BIOS as needed, boot an OS and/or install it to the hard disk image. Then install your games on the hard disk image to play it.
