Remove the top and/or the remove the bottom, as explained above. Then lift up the can so that the desired width of strip is exposed above the lip of the sleeve. Lock the can into place with one or more pushpins inserted in the sleeve's top anchor holes. (This is an essential step.) You'll need to brace the inside of the can with your non-anchor-hole-popping-hand, but don't poke your other hand's finger with the pushpin as it punches through the can's metal.
Make a cut downward cut into the side of the strip. Then make a tiny cut perpendicular to the first cut as near to the lip of the sleeve as possible. This makes it much easier to start peeling off the strip.
Then peel the strip off like an orange. Keep your pressure at the point of the tear, but be gentle, since not much force is needed. Be mindful of what the loose end of the strip is doing as you peel. Finally, trim any remnant off with scissors.