Extract the downloaded archive to a folder on your computer. Organize the ROMs in a way that makes sense to you, such as creating folders for each game or genre.
You're interested in downloading a Neo Geo ROM pack! Before I guide you through the process, let's clarify a few things: Neo Geo Rom Pack Download
With that said, here's a step-by-step guide to help you find and download a Neo Geo ROM pack: Extract the downloaded archive to a folder on your computer