When you have an available account balance you can apply this balance towards a new campaign or refund it to your card on file.
If applying your balance to a new campaign you'll first need to create a campaign and leave it in Draft status. You can do this by going through the normal campaign creation flow, but not completing campaign funding on step 3.
If you have no campaigns in Draft status the Apply Balance to New Campaign button will be grey an inoperable until you have created at least 1 Draft campaign.
Once you have a campaign in Draft status the Apply Balance to New Campaign button will be operable. Keep in mind however that your account balance must be sufficient to cover at least 1 day of rebates on your Draft campaign.
If for example you create a Draft campaign offering 100 units per day with a total rebate cost of $1,000 but you only have $500 in available account balance, you will not be able to apply your balance to this new campaign until you reduce the units offered to total the same or less value than your account balance.