You have to factory reset the TV, create your own account at https://my.roku.com, and then link the TV to that account when you go through the setup process. You must have a physical remote. You can either get a Roku Voice Remote available online or many big box stores or get a universal remote that supports Roku TVs. Roku "simple" remotes do not work with Roku TVs.
How to factory reset your Roku® streaming device | Official Roku Support
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.