You remove the plastic lid, pull open the "pull top" aluminum, put the plastic lid back on, and microwave it. This leaves an aluminum rim around the top of the cup, with the plastic lid over it.
I did as instructed, and it sounded like there was a war battle inside my MW oven. That container actually jumps around and sounds like it's sparking, but that plastic lid covers the metal rim. Somehow this seems unsafe for the MW oven. (as far as doing damage to it). The food does get hot quickly though.
I'd think the company that makes these things should know what they are doing, but I'm concerned about doing damage to my MW oven. Actually I probably wont have to worry about it anymore, because the food is pretty dull and tasteless, despite being a quick and easy snack.