Where to manually download Software Updates for a Mac
I recently needed to install some Mac OS X Software Updates on an older machine that couldn’t connect to the internet. This means the option to just go to the Software Update installer built into Mac OS wasn’t happening, but I knew that upgrading the system software was likely to help alleviate the problem. If you’re ever in this boat, all you need to do is visit Apple.com’s Software Updates site and you can manually download any of the available software updates as package files; iTunes, Aperature, Mac OS X, firmware updates, security fixes, any update Apple releases is available for download. Then all you need to do is copy these files from the machine you downloaded them onto to the machine that can’t connect to the internet, in my case I just used a USB key and installed them to the troubled MacBook from there.
You can download any of the Mac OS X Software Updates directly from Apple at:
Apple Support: Software Updates & Downloads
I ended up fixing this Mac’s wireless problem by upgrading to the latest version of Mac OS and deleting it’s network preferences. An easy enough fix assuming you have another available machine to access the downloads with.

How would i install the software update from the USB?