We know by now that the title is very important here. It must be since Stevens repeats it twice in a short two-stanza poem. We also know that it's a silly-sounding title, even though it's still important. (Come on—can you imagine some guy sitting on a throne made out of cookie bits and sprinkles?) There's some significance here in the idea that, although the title sounds silly, it's getting at a pretty loaded idea.
We get that emperors are hotshots with iron fists. But this emperor is one with an ice cream in hand! What's he in charge of then? How about pure, unadulterated enjoyment? We mean, just try to worry about life while eating ice cream—we dare you. Can't do it, can you? That's because that enjoyable sensation attunes you to the moment, that fleeting yet fundamental experience of being a human being on planet Earth.
Once you get beyond that fundamental truth, everything else, really, is a kind of window dressing. It's all so much… appearance. To heck with that, this poem tells us. Just enjoy the experience of being. Need a role model? Well, we can' think of a better one than our titular friend: the emperor of ice-cream. He's an inspiration to all of us not to sweat the small stuff, and to rule our own empires of simple, unadulterated truths. We'll start our rule with two scoops of peanut butter and chocolate, please!