Put any files you want to use in your VM (virtual machine) into that folder.
Restart the app.
On the VM's (virtual machine) desktop, find the "Unix" volume and double-click to open it.
Find the "macintosh.js" folder, which now contains all your files.
Files will be copied over when you start your VM (virtual machine). They are not synchronized while the VM is running. However, any changes made to the "macintosh.js" folder in your VM will be saved to the corresponding folder in your home directory once you shut the VM down.
Getting files out of machine
On the VM's (virtual machine) desktop, find the "Unix" volume and double-click to open it.
Find the "macintosh.js" folder.
Copy any files you want to move out of your VM into that folder.
If you're curious, you can enable developer tools. They will automatically open when you start the app. Some transparency features
will break. Restart the app for this change to take effect.