How do you input a WEP key for decryption in Wireshark preferences?

I can bring up Wireshark preferences. I can select the Protocols and indicate that decryption should be used. I can click to edit the button for the decryption key. I can select WEP as the key type. But, I can't get the key itself to input. I have searched the reference documentation and have not found this level of detail. What is the trick?

Any guidance is appreciated - bab