PayPal button - drop down menu

I tried to insert a button from PayPal to my site, however it says that you have to use the HTML part of the site to insert it. I tried that and all that happened is the code itself showed up not the button and then the whole site froze up and I could not do anything. Is there anyone who can walk me through this easy steps from point A to D or whatever. I had the HTML box down where I wanted it, but when I tried to covert it after publishing or saving, it was still the same encrypted code, no button!!