Follow these steps to make a withdrawal from your UGMA account:
Log in to your account.
Click on the account you'd like to make a withdrawal from.
Choose "Make Withdrawal."
Type in the amount and add a brief description if you'd like.
Hit the "Submit Withdrawal" button.
Just a heads-up: you can make only one withdrawal at a time per account. If you've got one in progress, hang tight until it's done before starting another. However, depending on how far along the withdrawal is, you may be able to cancel it. Read more on how to cancel a withdrawal here.
Note: Withdrawals cannot be over the daily limit of $50,000.00.