On the Store Manager startup you will see registration form. In this form you can specify the license key that you have purchased. In case this key was already used on another PC, you will be offered to reset your key and register on this machine. Note, the key will stop working on the original machine.
By clicking on this button you will clear old license information, while license keys won't change.
Note: If you need software to be used or installed on the other computer as well as on the old one, you have to purchase additional license key for it.
Important note: If you move license to other machine, it is recommended to save all configurations to be able to load them on the new PC without setting them up again. You can find how to make it here - https://support.emagicone.com/009334-How-to-transfer-data-from-Store-Manager--to-another-PC