I go to a Chabad synagogue where everyone wears black belts called gartels. When I went on a Chasidic tour to Williamsbourg I bought a black Gartel. Now that Yom Kippur is on its way I have bought a white one that I will also use on Peisach. Although the nice man who ran the store put the Gartel on me I do not remember how to put it on. Is there a specific way to put it on you?
1.The gartel is wrapped around the stomach as many times as needed 2.The ends are tucked into the part already wrapped around the stomach which creates two loops. This can be one at a time. 3.The ends are then put through the loops that were made and pulled tight 4.The remainder hangs down to the sides.
For me the challenge is finding a gartel that is the right size. I often find that the gartel length ends up with the left overs hanging by my sides feel too long or too short. If my written instruction are unclear I suggest asking someone in your shul to demonstrate. I'm sure they will be glad to help.
This is how I put on a gartel and how I have observed others doing so as well. I don't know of any halachos around how to put one on and I'm not sure there are any but this is the method I follow and see others following as well.
May all your tefilos be accepted for good by Hashem.
The idea of a gartel is just a belt to make sure one's clothes are tight to his body (source) in order to prevent the issue of לבו רואה את הערוה, or his heart being able to "see" his genitals (laid out here). Most Ashkenazim don't wear a specific gartel, they just rely on a regular belt or clothes with a tight waistband. Chassidim do wear a gartel because they keep the dress habits of older generations, but there is no halachic specification for how to wear it. The instructions in the previous answer are practical only.