If you are a present customer of coinbase and you want to transfer from coinbase to gdax, there here is some steps which you can follow to process. Visit Coinbase official site and jump on the Gdax Exchange, you will see deposite and withdrawl button on left site of the page in corne. If you want to deposite then click on it and you will see pop up to deposite funds. After you have complete these steps you are going to transfering from coinbase to gdax . You are almost done, now choose a coinbase wallet as your source of funds , Finally enter the total amount that you want to transfer and click on deposte in the last steps.
For more info visit :- https://www.gdaxlogin.com/