The Samples available will have a little grey icon in the Sample column. I suggest you select parts that have a /P or /SP part number since that indicates DIP package.
You can get new sample orders every month and sometimes get more than one per month. If you aren't using this system to stock your own lab and develop with Microchip PICs then you are missing out on a great opportunity. I don't know of very many companies that make it this easy and Free!