If you click on a regular RSS feed button on a website then usually it opens up in a new web browser and is full of programming code. (If you click on the feed button or link on this site you will be go to feedburner.com and be able to read what you would currently receive if you were a subscriber.)
You will then need to choose which RSS reader you would like to recive the feed on. That is because RSS feeds are meant to be read by dedicated RSS readers. There are many free readers available online and a quick search will help you track down one that appeals.
When you find a website that you want to subscribe to, click on the site's “RSS” or “XML” button on their homepage and most RSS readers will instantly allow that feed to be added. Some readers require you to cut and paste the URL of the feed into the program.
Once you've added it then it will instantly be available and updated. If you change your mind and want to stop the updates then all you need to do is delete the feed or URL from your reader.