Scroll down if necessary until you can see the cargo container.
Next to its picture, you should see a drop-down box with the number of items in it. Select the amount of items you want to remove, then click the "remove" button.
If it's a different form of storage item such as a backpack or trunk:
Click the "Items" button.
Scroll down if necessary until you can see the backpack/trunk/whatever your item is stored in.
Next to its picture, you should see a button called "view contents". Click it and find your item.
Click the "drop" button next to your item.
In either case, you item will now be on the floor.
It's also possible you're looking at the item in your inventory, and you're not actually at your item's location. n that case there's nothing you can do, since you can remotely remove an items from a container.
I followed thse instructuons an got this message
An Error type: Exception with the Message: Unable to withdraw item from crate: Not enough weight/vol capacity in the container to hold this entity (2 != 4 && (0.0300 * 1) > 0.1) || (5.1000 * 1) > 1) Data: ContainerID: 7570758, ContainerType: 6. has occured. It has been stored as Error 27940.
If this bug has not been reported (check first, please), report it to the bugtracker at http://bugs.swcombine.com/
Or, the error message you should be getting is bugged and not showing correctly. Check to make sure the entity you are in has enough space and weigh capacity left for the item you are trying to remove. If there is not enough space then you will not be able to remove anything in the crate.