Dropdown box: Click on the box to expand it. If there are a lot of options in the menu, it can be filtered by typing in the text box and scrolled using the middle mouse button or the scroll bar on the right of the list. Once you have found the item that you would like to select, click on it.
An example of a dropdown box with some text typed in to filter the options.
Database Search: Type what you would like to search for into the text box on the right of the search button, or leave it blank to return all available options.
An example of the database search with text entered into the search box.Then press the search button to open the item selection form, if there are items matching what was searched for, there will be buttons with the names of the items next to them. Use these buttons to choose the desired option, and finally use the "Select" button to add them to the filter criteria.
An example of the item selector.