how do i upgrade leopard to lion?

First you would need to buy Snow leopard - call Apple to get an install disk. Then, since Lion is no longer availaable at the app store, you can place the order for that with Apple as well - they will email you a redemption code to use at the app store. So, you will need to install Snow Leopard, update it to the latest version (which includes the app store), and then go to the app store to redeem/download Lion.

But...... first make sure your machine meets the requirements:

http://support.apple.com/kb/HT4949

And, the 2 GB RAM mentioned are an absolute minimum - 4 GB would be a far more realistic minimum.

call Apple to get an install disk

Best is to just buy it from the Apple Store.

Thanks, I didn't realize they still had it in the store.