After landing on the Advanced Search screen, you will need to decide if you want to search all of the OCLC databases or only certain databases.
If you want to select all of the OCLC databases, simply click on the "Select All in Group" button under the FirstSearch heading.
To select individual databases, click on the little arrow next to the FirstSearch heading.
Choose the desired database(s) by clicking on the box next to the database name.
Click on the "Save Changes" button.
You are now ready to search.