10.10 isn't an update, it's an upgrade. Which means you have to go to apple dot com and ask for it.
Best you get some advice about doing so, first, though -- lots of folks have had problems with 10.10.
"Gilly" is right on the money about Yosemite being an upgrade not an update. But you need to go to the Mac App Store (or just App Store) to get it. Actually you can go to Apple.com too...there's a link there that will take you to the App Store.
Thanks all. I figured it out right after I posted. I have upgraded and all seems to be working ok. We'll see how it goes. Is there anything, in particular, that I should be looking at as far as problems are concerned? Thanks again for all of your quick replies.
You may see some issues with Mail (particularly if you use Mail for Gmail or Outlook), Wi-Fi (occasionally issues reconnecting after sleep, or abnormally slow performance) or Bluetooth (occasional refusal to connect).
I have been using Yosemite for many months now and have only seen issues with the last one (occasional Bluetooth bullheadedness, a restart fixes it but annoying), but others have reported these issues. It's not apparently universal, however, so you may never notice anything.
There is a whole raft of new tricks your Mac can do if you have an iOS device around and a recent-model Mac (2012 or later), and a whole raft of general improvements. But as I find I have to remind people a LOT these days, x.1 or even x.2 is early days with a new major OS upgrade.