You need to get miniVMac, a Mac plus ROM file, and the original images of the original disks. If you want something that can do more than just play DC (or want to make a hard-disk image) then you will also want to download System 6.0 (other versions work, but this is the most robust IMHO).
BDC is exactly the same a DC (covered below) just obviously you need the BDC images - otherwise what you do is identical. If you go down the making a hard-disk image, you can put both DC and BDC on the same hard disk. I used a 20MB image for my disk, which was plenty.
There are isntructions posted by gruz here
aimed at windows users. It details how to get some of it going though (you don't need to do nearly as much if you're already on a mac).
The first is freely download-able (google) or go to their website
The second is not, but can be found with suitable use of google. It can also be quasi-legally dumped if you still have access to a Mac Plus
The third you can make yourself if you still have the original disks and access to a floppy drive (just use DiskUtility). If not, again, google is your friend. Gruz recommends looking here
System 6.0 you can get direct from Apple as a free download. In the legacy support area of their site, although (as ever) just use google if you can't find it.
Once you have those assembled you need to do the following:
- Extract MiniVmac to somewhere on your hard disk
- Copy the rom file into the same directory as the miniVmac program and make sure it is called "vMac.ROM" (no quotes)
- Either drag the DarkCastle disk A image straight onto mini vmac and get playing or if you want to create a hard disk, read on:
- create a blank image (or download one, mini-vmac may even come with some, or link you to them... if not, as ever, google)
- drag the system 6.0 install disk 1 image onto mini-vmac (make sure it is uncompressed and not mounted in the finder)
- mini-vmac should boot to the sys 6 installer (ain't it quaint? ;)) - drag the blank on top of the mini-vmac window, and it should appear as a target install disk
- run the install, dragging any other sys 6 disk images to mini-vmac as and when requested
- shut down/reboot the emulated mac-plus
- drag the new hard disk image onto mini vmac. It should now boot you to system 6.
- create a new "Dark Castle" folder, and drag on the DC images
- copy the contents of the images into this folder. You don't need the 'system' and 'finder' files from disk A, just "Dark Castle" itself and "Data A". From disk B, you obviously need "Data B".
- double click on dark castle
I'm assuming a reasonable amount of being able to find your way through things here. If you get stuck or need to ask questions, feel free to post.
Good luck, and happy playing :)