It’s more a ZEN-Core thing. And even then only the Jupiter/Juno-X and GO:KEYS stuff. No FANTOM. No MCs 101 or 707. It’s kind of a weird duck.
You could either buy the plugins (i.e. purchase a “lifetime key”), subscribe to a Pro cloud membership (which gives you access to two plugins of your choice), or subscribe to an Ultimate membership (which gives you access to all of them).
Then you’d install the plugins and open them up in your DAW. After connecting the System-8 via USB, you click the PLUG-OUT button in the plugin’s UI:
If you bought a lifetime key to the plugin, that’s all there is to it. You’ll always have access to the plugin so will always be able to do this.
If you have a Cloud subscription, then you’ll have access to the plugins as long as you pay the subscription. When you stop paying, the plugins will open in “demo” mode and the PLUG-OUT button won’t work.
Whatever is already on the System-8 will still be there and will work as usual, but because none of your plugins will have working PLUG-OUT buttons, you won’t be able to install anything new.