Hello, I’m Nathan, and I’ll be assisting you today. My livelihood depends on your positive feedback, so your satisfaction is my highest priority.
Sorry to hear you’re having trouble.
There are a few steps needed here for the initial setup process.
You need to hook the roku up to the tv via hdmi cable. This is a separate connection than your existing soundbar, cable box, etc.
Don't change or disconnect anything else.
Hook roku to the tv, lets say on hdmi2 for example, then set the tv to the corresponding input mode (hdmi2, or wherever you've plugged the roku into).
From there you'll press the Home or Ok button on the roku remote to wake up the roku box.
You'll see the roku on screen setup menu, which has an auto setup wizard to guide you through the initial settings. It will first ask you to pick your home wifi network name from a list and then enter your wifi password.
Once connected, it will ask you to register your roku. For that you'll be presented with a code number on the computer screen, and you'll go (On the computer) to roku.com/link
There you'll enter that code from the tv, and either sign in to your existing roku account, or set up a new account.
From that point you can begin using the roku normally, adding "channels", opening apps such as netflix, etc. The first time you use each app (such as netflix) you'll generally be prompted to sign in to that particular app as well, as many require a subscription/account to use.
Let me know if you get stuck,