Step 1: Follow the link
https://binance.com/en/square/post/21761942594842
Step 2: Click open in Binance
Step 3: Make sure you have 0.01 BNB in your wallet (approx 10$)
Step 4: Select F3B
Step 5: Click vote
Step 6: Confirm
Voila that's how you vote

PS: You have to hold that 0.01 BNB for 1 week until voting ends for your vote to count