First, you have to troubleshoot the following:

The goggle is either not properly fitted to your eye sockets, not tight enough, or the angle at which you dive is making them fall off. The last option is probably the most likely and the hardest to fix.

[a] You’re probably hitting the water with your goggles. You want to hit the water with the top of your head. It is easiest when you tuck your chin.

[b] You need to tuck your head essentially under your outstretched arms. That causes the force of water to hit the top of your arms and the top/back of your head.

Once you get it once it will become a lot easier!

Good luck!