Cheetah Tool is a software that enables you perform operations like network unlock on Samsung and LG devices. It doesn't require a hardware box / dongle to use, just an activation and (or) server credits. For this guide, I'll be using SIM Killer Pro as it doesn't require an activation, just credits.
Visit https://cheetah-tool.com/en/resellers to either buy a license or credits (SIM Killer Pro requires only credits) from a reseller. Ensure to use or supply the email address used to signup at the Cheetah website
Once your account or credits are setup, you should get an email from the reseller