How do I buy and install a router?

Can you please guide me through the process of purchasing and setting up a router? I'm not very tech-savvy and I'm having trouble understanding the steps involved. Can you break it down into simple, easy-to-follow instructions? Specifically, I'd like to know what factors I should consider when choosing a router, how to make the purchase, and what steps I need to take to install and configure it. Additionally, are there any security measures I should take to protect my network? Your help would be greatly appreciated.