Grampian;
Don't worry too much about it...I was in the same boat as you 3 years ago. Literally. (Tanzer 22, never flown spinnaker)
So - first thing, congrats on a great boat. T22's are an absolutely dynamite boat to learn on.
Next - make sure you have all the stuff you need to do this:
Spinnaker, Spinnaker pole (long aluminum pole with jaws and spring pins on each end.), a halyard that you are not using to hoist either main or jib, and 2 long lines, preferably with snap-shackles. You should also have a 'pole up' and pole down' line rigged on your boat. do you? if not, it's not too hard.
if you have all of that, you're good to move on to the next step. Grab the spinnaker pole, and figure out how to hook it to the mast. There should be a hoop there. Hook up your pole up and down lines, and then go back to the cockpit (do all of this at the dock, or while drifting in no wind.) and play around with the controls - raise and lower the pole a few times.
If all of this is OK with you, it's time to make the big leap.
Go to You-tube and search for spinnaker sailing. You will find a bunch of yahoos and horrible videos about crazy winds. Don't watch those - you'll scare yourself silly.
You should also find a couple of North Sails spinnaker tutorials - one by a guy named Tom Whidden. They are made in the 80's, but don't let that bother you - super instructions.
They should answer most any questions you have.
watch them. then watch them again.
Now - go try for yourself. do it on a light wind day, and you won't hurt your boat, or yourself.
Enjoy!!
Andy