First, if you have not already done so, download the appropriate version of the Mini vMac compiled application for your operating system from the download page. If your web browser doesn’t automatically expand it, do so manually.
Next you will need a ROM image file from a Macintosh Plus. This file should be named “vMac.ROM”. A utility such as “CopyRoms” can be used to obtain this file from your Macintosh Plus. (If you don’t have a Macintosh Plus, you could check the “Where to buy an old Macintosh” page.) (And before you ask, the FAQ page has a section about ROM images.)
Next, you will need a bootable disk image for the Macintosh Plus. You can download the two System 6.0.8 install disks from Apple: “SSW_6.0.8-1.4MB_Disk1of2.sea.bin” and “SSW_6.0.8-1.4MB_Disk2of2.sea.bin”.
Use any modern version of the program Stuffit Expander (now from Smith Micro Inc.) to get the disk image “System Startup” from “SSW_6.0.8-1.4MB_Disk1of2.sea.bin”. (If you can't use Stuffit Expander, some alternatives are listed in the footnote. *)
Move the “vMac.ROM” file into the same folder as the Mini vMac application you have just downloaded. Now launch Mini vMac. The Macintosh and Windows versions can be launched by double clicking on the application’s icon. In Linux you can use the command line to set the current directory to the folder containing the application, and then issue the command: “./minivmac”.
Mini vMac should open a window, filled with a gray pattern, with a picture of a floppy disk in the center, with a blinking question mark on it:
Drag the icon of your bootable disk image, “System Startup”, onto the Mini vMac window. The emulated computer should boot from this image, starting up the Finder, with a menu bar at the top of the emulated screen:
When you’re done looking at this, choose the “Shut Down” command from the “Special” menu on the emulated screen:
Then click on the close box of the Mini vMac window to quit the application.
If you find Mini vMac useful, please consider helping the Gryphel Project, of which it is a part.
Next - Using Mini vMac
(*) Alternatives if you can't use Stuffit Expander on your computer (or don't wish to install it):
The simplest alternative is to use the computer of a friend that has it installed.
You can use an old Macintosh to expand it (i.e. such as your Macintosh Plus.) The file “SSW_6.0.8-1.4MB_Disk1of2.sea.bin” contains a Macintosh file encoded in MacBinary format, preserving Macintosh specific information. You can use a program such as "binUnpk" to extract the program “SSW 6.0.8-1.4MB Disk1of2.sea”. This program is a Stuffit Self Extracting Archive. Running it on an old Macintosh will get a disk image file named “System Startup”.
Instead of a real Macintosh, you can use the program Executor, which can run some 680x0 Macintosh software without requiring any software from Apple. Though it is no longer developed or supported, it currently may be downloaded for free. It comes with StuffIt Expander 4.0.1 which can extract the program “SSW 6.0.8-1.4MB Disk1of2.sea” from “SSW_6.0.8-1.4MB_Disk1of2.sea.bin”, and then “SSW 6.0.8-1.4MB Disk1of2.sea” can be run to get the disk image “System Startup”.
If you happen to have any sort of disk image that can boot Mini vMac (i.e. containing system 7.5.5 or earlier), then you can use Mini vMac to extract the archive, to get a clean copy of official Apple system software. You will need a large enough blank disk image (see “Blanks”), ImportFl to import the '.bin' file, binUnpk to decode the '.bin' file (to get the '.sea' file that you run), and ExportFl to get the extracted disk image back to the host computer.
“Samir” points out that The Unarchiver, a free and open source utility for OS X, “can extract .sea files as well as .bin files and a lot of other archive formats”.
“Bjoern” points out another alternative for Intel Macs. System 7.0.1 is available from Apple’s older software page in '.smi.bin' format. '.bin' can be decoded by any Mac version of StuffIt Expander, and probably other programs as well. This results in an '.smi' file that can be opened in OS X, mounting a disk image that contains 6 disk images that can be used in Mini vMac.
Previous versions of this page recommended using “SSW_6.0.8-800k_Disk1of4.sea.bin” through “SSW_6.0.8-800k_Disk4of4.sea.bin”, which have the same system 6.0.8 software, and which are also available from the same older software page. Thanks to Ryan Schmidt for pointing out that these 800k disk images are packaged as DiskDoubler Self Extracting Archives, which can not be expanded with Stuffit Expander, while the 1.4MB disk images are packaged as Stuffit Self Extracting Archives, and can be. The 1.4MB images can not be used with a real Mac Plus, but the emulated Mac Plus of Mini vMac can use them, because of the replacement disk driver.