If you have not done so yet, deploy your wallet: Guide
Open Crystal wallet and click on WTON token section
Click "Send" and specify WTONs amount you want to convert in TONs.
As a recipient, specify Vault address (0:d0936a9fc29b5175487208b1d07ab8042ce7ddbc2de7e271c4087ca833b865cc)
Make sure you have some TONs to pay fees
Send transaction with a comment. After confirmation, your WTON balance will decrease and your TON balance will increase.
If you are using the Chrome Extension, make sure instead you enabled Notify receiver.