This documentation applies for JabRef 3.7 or later.
To fetch entries from zbMATH, choose Search → Web search, and the search interface will appear in the side pane. Select zbMATH in the dropdown menu. To start a search, enter the words of your query, and press Enter or the Fetch button.
Then, the results are displayed in the import inspection window. In case an error occurs, it is shown in a popup.