The following YouTube video explains how to use DfontSplitter - http://www.youtube.com/watch?v=S3mRSuqyxpc

Alternatively, follow this text guide. First of all, launch DfontSplitter, by double-clicking it in Applications (or wherever you placed it).

Click the Add button below the Source Files list and choose a .dfont file using the browser, or drag in one or more .dfont files from the Finder and drop them on the list area. Under Destination Folder, click Choose and select a folder where the extracted files should be placed.

Click the Convert button.