Q: I would like to upgrade my MAC OS X 10.6.8 to any latest MAC OS.

in your updates, does it specify a software update, if so.

on the update that appears, there should be a drop down arrow or 'show more' option on that update.

select that and see what it provides.

click update, and then it will tell you your requirements, and/ or it will let you know if you can upgrade

or

OS X El Capitan requires one of the following Mac models and versions of OS X. It also requires at least 2GB of memory and 8.8GB of storage space.

• iMac (Mid 2007 or newer)
• MacBook (Late 2008 Aluminum, Early 2009, or newer)
• MacBook Pro (Mid 2007 or newer)
• MacBook Air (Late 2008 or newer)
• Mac mini (Early 2009 or newer)
• Mac Pro (Early 2008 or newer)
• Xserve (Early 2009)

• OS X Yosemite v10.10
• OS X Mavericks v10.9
• OS X Mountain Lion v10.8
• OS X Lion v10.7
• Mac OS X Snow Leopard v10.6.8

To find your model, memory, storage, and version of OS X, choose About This Mac from the Apple menu. Here's a shortcut: If your Mac is using OS X Yosemite or Mavericks, it can use El Capitan. Otherwise, make sure that your Mac meets the other requirements.

Hi,

According to Mactracker, your Macbook Air -- original OS 10.57 -- can run the latest OS X, which is now El Capitan and is free.

However, you have only 2gb of RAM, so the performance may not be good. You could back up everything and try installing El Capitan and if not satisfied restore from backup. The RAM on a Macbook Air cannot be upgraded.

Regards

Here is how to upgrade to El Capitan, should you choose to do so:

Upgrade to OS X El Capitan - Apple Support