Just select a file from the list, and double-click it. Alternatively, with a file selected, click File|Open from the menu. If WordPerfect is associated with the selected file, it will open in WordPerfect.

 

Otherwise, the file will open with whatever application the file is associated with. If the file has no associated application, the standard “Windows cannot open this file:” dialog will appear, and you can select the application to open the file.