Device drivers and VMs are stored in the "Drivers" directory. If you find that your device folders exist but are empty, download the device files from https://github.com/tuftsceeo/botspeak/tree/master/Devices
Click on the Device that you'd like to download files for, then find the "Download ZIP" button, or use git to clone the repository.
You can always use git to download the entire BotSpeak folder and all device files with "git clone --recursive https://github.com/tuftsceeo/botspeak.git"