You have to get your balance down to $199 to trade ANY future draft pick. You can do so directly from your player dashboard. The balance will always show the entire year balance unless you pay down on it. Paying it down to $199 will give your team rights to offer and propose your future picks.
There will be a text link on your dashboard under the BALANCES OWED section that says DFWC XX (or whatever league you are in) and then a year dues column with your balance. You click on it and pay.
Also remember, this must be done from the primary manager's e-mail address.