You can activate your license on up to two devices at a time. A "device" is either a computer (which can host a virtual iLok USB key), or an actual physical iLok USB key. The iLok USB key would need to be associated with your iLok account to which you made the Soundtoys purchase.
Please note that the second activation is intended for the same user. If you have multiple users running Soundtoys simultaneously, you should purchase a separate license for each user, per our license agreement. Click here for information on Soundtoys site licenses.