Help getting started with Roku devices, including setup, connecting your device to your TV, linking a Roku device to your account at my.roku.com/link, adding channels, subscribing to services, and more.
Does the TV have HDMI inputs? If not, then you would need either an Express+, or buy a separate HDMI to composite or component converter. Could almost be cheaper to simply buy a new TV.
The 2017 version of the Express + (model 3910) has component output, but the current version released in 2019 (model 3931) does not. If you need this capability, check your purchase carefully to be sure you get the model you need. (A pox on Roku for changing features but keeping the same model name... )