You can follow instructions step by step in documents in this link: https;//ispyoo.com, menu Download or Download Center.
For example, for android devices, visit this link android.ispyoo.com
Notes: Please keep in your hand physically the target device, download, and install iSpyoo into that device. DO NOT install the app ON YOUR DEVICE.
For more details for how to install: https://ispyoo.com/how-to-install/