How do I upgrade from Snow Leopard to the next level Lion ?

Choose About this Mac from the Apple menu, check if the computer has at least 2GB of RAM, and if it does, click here and order a download code for Lion 10.7.

Back up your data and check your applications for compatibility before upgrading. In particular, Mac OS X 10.7 and newer don't support PowerPC programs such as versions of Microsoft Office prior to 2008.

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I am doing this upgrade so I can install Norton.

Bad reasoning. You should avoid Norton. There are no active viruses for the Mac. Certainly nothing that would prevent you from Upgrading to Yosemite, if your Mac meets the criteria. You would have to have a MacBook Pro 3.1 or above to use Yosemite.

If you have a MacBook Pro 2.1, you're probably better off sticking with Snow Leopard, as Lion is a dog not worth $20.

Once again, I recommend not installing Norton.

This is why you need to explain, fully, what you're doing in your first posting. I'm sure that Niel would have not made that recommendation if you had mentioned why you wanted to do it.