When a business buys goods or services on account instead of paying cash there and then, its suppliers are its creditors until it pays them. Enter in your cash flow forecast any payments that you will make to your creditors (including VAT) in the months in which you will pay them.
'Payments to creditors' refers mainly to items like retail stock and other goods or services that businesses buy in to sell on to their customers. As this is not a 'buying and selling' business like a shop or wholesaler it's quite likely that you won't be making any payments to creditors. If this is the case, your figure for Payments to creditors will be zero.