Get a working, inexpensive meter such as the WalMart ReliOn Confirm, Confirm Micro, or Prime, matching test strips, and 26-28 gauge lancets.
Before you test your cat, practice a bit.
Practice on fruit - apples, grapes, etc to get a feel for it.
Test on your self.
This will take care of some of your nervousness.
Now you're ready to start working with your cat.
Get some low carb treats, such as plain freeze-dried meat or poultry.
Set up your testing area - a half bathroom works well to confine the wiggly cat.
Condition/train your cat - the first few times, go in the bathroom with the cat, say "Test time", sit down with the cat on your lap, massage the ears a bit, give the low carb treat, release the cat and open the door.
Take a thorough look at the ear. See the vein along the outer edge? You will use the lancet to make a small prick between the vein and the edge of the ear.
Push the test strip part way in the meter.
Brace the ear with a folded tissue, prick the ear, and snag the droplet on a clean fingernail.
Blot the ear with one hand while you push the strip all the way in.
Touch the absorbing edge of the strip to the droplet.
Record the results in your spreadsheet.