1- you make general free-form dua all day before Maghrib (optional).
2- you break your fast at Maghrib time,by simply saying bismillah like one always does when you eat (required).
3- you say this supplication (in the video) right after eating/drinking something (recommended).
4- you make general free-form dua (optional).
5- you continue with your meal (optional)
The common mistake is to hault breaking the fast by making general free-form dua, or by saying this specific supplication or others before breaking your fast. This is incorrect, when it is time to break the fast, break the fast do not delay it; and after which say this duaa.
This supplication is an authentic narration, there are other popular narrations but they are weak.