Hi,
You have to add your data element first to your worklist by clicking "MY Worklist" button SE63.
Give your Data element name in the next screen in the object name and press the cancel button
It should give you a popup to save that in a worklist.. Select the source and target language correctly and then press the green arrow button at the buttom.
Then try to do the same way that you have been trying. It should open a different screen now.
R