How do I find the proper software to download from the web for windows 8 to replace my current windows 7?

You can't upgrade for no $. But you could (month ago) sign up for Windows Upgrade Offer to upgrade from Windows 7 to Windows 8 Pro for just $14.99, now it is $39.99 and it's no longer the upgrade offer.
If you want to get Windows 8 for free*, that is considered as a crime and piracy, so please do not try to do that.

You can go to:
https://plus.google.com/106859544546193125745/posts/LdmdW9659fj, here you can find keys of any windows products, it is genuine and cheap. Once I have bought a windows 7 pro key on that website, it is really worthy and helpful.I hope it can help you guys.

There is no harm in trying this page, i got a good key here, it is good and the customer service is also good, i feel happy for this shopping online. www.fastbackorders.com

This website does help me a lot. If you are in need of windows product keys or have other problems, you can have a look at it. Hope it can also help you. www.fastbackorders.com

If you need cheap windows 7 product key.You can click here: https://www.facebook.com/pages/Cheap-Windows-7-Product-Key/1591144934502317.My key bought here. The key working properly and it cost me a little money.