Plug the iPod Touch into your computer. Let iTunes open automatically, or if it doesn't, open it yourself.
iPhoto might try to open as well, just close it or push it aside for the time being.
In iTunes on the left bar you'll see your iTouch listed. If you haven't synced it before, you'll need to register it, including giving your iTouch a name. Doesn't take long.
Then look at the "tab" type markers above indicating the pages for Audio, Photos, Apps, etc. I think Calendar and Mail and some other tings are on the second page. Scroll down to see them all.
Set things how you like them, and then go to the bottom of the 1st page and press "Sync". It might or might not ask you a question or two, just answer to your liking, and let it go on to sync then.
When done, you need to click on the little, tiny arrow on the left, across from the name of your phone. Be sure to do this before disconnecting it. Then you can disconnect and you're good to go.
Many people like to sync once a month, some more or less often. If you add to your calendar often, you'll probably want to sync more often.
If you're using iCloud - I don't know. Haven't tried syncing yet with iCloud. Good luck.