How to create DDoS attack (on yourself)

Month ago, I had www site about game (Heroes of The Storm). Everything was fine, untill someone who want to kick me off started to DDoS me, unfortunatelly mine hosting was not prepared for that, thats why I had to stop hosting that site and earn some money for better server.
Now I had bought private VPS on OVH and I want to run my site again.
Firstly I want to check if I am protected enought by attacking myself and check various software to protect my VPS, thats why I want to know, how I can do that? That guy had destroyed my previous site by sending about 5Gbps unwanted data untill I turned my site off. I want to do simillar attack from mine PC's to check if OVH VPS will handle that, someone can give me a tip which programs I can use to do that?