Guymager can be started by using the menu in Kali and by clicking on Applications on the side menu, and then click on Forensics and scroll down to Guymager:

Guymager can also be started using the Terminal by typing guymager. You may also try the sudo guymager command. Once started, the default locations of the log file and configuration (cfg) files, which can be changed if required:

The Guymager application runs and then displays the existing drives recognized in Kali Linux. As seen in the following screenshot, the details of the 2 GB flash drive being used are shown, including the following:

• Linux device: Recognized as /dev/sdb
• Model: USB_Flash_Memory
• State: Shown as Idle as the image acquisition has not yet begun
• Size: 2.0GB

Should your device not be listed in Guymager or should you need to add an additional device, click the Rescan button at the top-left corner of the application.