1. Go to your Portfolio.
2. Select the bottle you received an offer on.
Can't select the bottle? Probably your bottle is already on sale. In other words, you already have an active sell order for this bottle. In order to change this sell order, you need to delete it (via Menu > Order overview) by clicking on the trash can. Once deleted, you should be able to select the bottle in your portfolio.
3. Click on Sell/Offer. You now go to the sell order screen.
4. If you select current price as strategy, the system automatically selects the highest bid as asking price.
5. Click on offer.