I hope you're a visual learner, because this is not as much a how-to but more of a visual study, or example in photographs, with a few short directions at the end.
But let's first ask the job your belt does. When was the last time you wore one? Was it when you lost 10 pounds after that stomach flue that was going around and desperately needed to hold your pants up? Or was it when you were wearing a white top, a white jacket, and white jeans and needed something to break up the monotony and you had a belt to match your luggage wedges? If your answer is similar to the latter example, than you, like me (who never gets a stomach flu, unless that's code for hung over) can also wear a shirt as a belt.
As far as directions go
1) Put on boring outfit. It can be boring by way of color, shape, or just needing a 'final touch'
2) Grab a long sleeve shirt in a complimentary color or pattern to your outfit
3) Tie arms of shirt around your waist
4) Congratulate yourself with a drink!