How to make my domain point to my VPS

I have recently bought here my VPS, i opened the firewall ports needed for my app to work on the internet, then i made my domain (bought on namecheap) point my VPS a day ago and it still doesn't reach my application, so i runned an open scan port and found out that the ports i have opened (even the app says that they are open) are in fact closed, what should i do? the domain is pointing correctly to my VPS public ip address