A dark waist band separates a visibly detailed pale upper section from a wider light skirt in this reference. The lower shape reaches around the knee area in the photograph and has several softly outlined vertical regions. The upper and lower contrast creates a divided appearance within the dress. It does not establish that the sections are separate pieces or that the waist band can be removed.
Try a comparable model without adding another belt first. Sit, stand and check where the existing division falls on you. If you want an additional belt, compare it afterwards rather than assuming the contrast needs reinforcement. A change at the waist can alter which upper or lower area draws attention, so inspect the complete outline again.
Use shoes and a bag you own for two versions. One can retain the dark waist as the strongest contrast; another can add a small matching or different accent. Decide which arrangement you enjoy with the intended outer layer. The photograph suggests a colour division, while actual length, construction and material details belong to the product you try.