To activate MTV on your Roku device using "mtv.com activate roku," first ensure your Roku is connected to both your TV and the internet. Create a Roku account if needed, then follow on-screen prompts to set up your device. Install the MTV app from the Roku Channel Store and open it to get an activation code. Visit www mtv com/activate, enter the code, sign in with your MTV account, and finish activation following any additional instructions.