To sell an object at your Home Station, you need to do the following:

1) Tap and hold the object you want to sell until it lights green.

2) Choose the Purse icon.

To sell an item from the storage:

1) Tap the item.

2) Choose the amount you want to sell.

3) Tap the Sell button.

NOTE! Not all items or buildings in the Storage can be sold. Some of them are unique and important for the gameplay.