To be able to run the Pfam Domain Search tool you must first download the Pfam database. The Pfam database can be downloaded using:
Toolbox | Sequence Analysis ()| Download Pfam Database ()
Specify where you would like to save the downloaded Pfam database. The output of the Download Pfam Database tool is a database object, which can be selected as a parameter for the Pfam Domain Search tool. It doesn't really make sense to try to open the database object directly from the Navigation Area as all you can see directly is the element history (which version of the Workbench that has been used and the name of the downloaded files) and the element info, which in this case only provides information about the database name.