You can only make a bid after having registered and after having transfered a sufficient amount of money into your portfolio account. You can easily transfer money by using iDEAL or Paypal.
Your balance showing immediately in your portfolio, you can make a bid for the bottle of your choice. The bid is valid until someone else makes a higher bid. The amount bid is "reserved" for as long as your bid stands.
So in case you wish to frequently buy and/or sell, we advise you to transfer a larger sum of money at once.