We have Roku on every tv in the house, the stick and boxes. The stick is the easiest to install, just plug it in the tv. Once installed you will have a channel selection . A list of every channel available will be shown. Some require a fee some are free. The home screen is different on each model of Roku. So it may be hard for someone to tell you go to this or that when your screen may be different. How fast and how much buffering will be determined by your wi fi. Slow internet is not for Roku. Set up is a breeze.
https://www.roku.com
The model I like the best is the Roku Premire for $80. There is one made for an older tv for $25. Lots to choose from.
Oh once bought there is no more fees or costs unless you want a paid for channel. You can take the Roku stick anywhere and plug into any tv with wi fi connection. Also you can have the remote for it on your phone! This comes in handy when you can't find the remote. LOL