how do I upgrade my processor on my MacBook Air?

I am trying to download a piece of equipment which requires at least a 1.8 Ghz processor. My MacBook Air has only 1.7 Ghz. Is it possible to upgrade it?

You don't. Mobile processors aren't necessarily made to be replaceable - often, they are soldered directly onto the logic board itself. Aside from the obvious voided warranty/extreme risk of damage to the board, you would need to either try the software for download to see if it'll actually run on your machine regardless of specs, or you will need to purchase a new laptop.

Sorry, the MacBook Air processor is soldered on and removing it would likely destroy the logic board. If you're looking for a powerful, yet relatively cheap laptop, get a used few-year-old MacBook Pro on eBay for a few hundred dollars (nothing too old, 2011 probably at the latest).