You have a couple of options. If you have access to the Roku account to which the device is already connected, log in to that account, scroll to the bottom, and Unlink the device.
Alternately, press and hold the Reset button on the device for no less than 30 seconds, then go through setup.
In either case, the device will be aware it's not tied to an account and walk you through setting it up. It will ask for your email address. Provide the address of the Roku account to which you wish to connect it.
Roku Community Streaming Expert
Note: I am not a Roku employee.
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