To make a new File Association, click the 'New' button, a new default item will be added to the list. Select the item and edit its properties as desired.
To delete a File Association, select the item, and click delete.
This is where you type in all the file types associated with the item your editing. File types must be typed as show above with commas separating multiple types.
The transfer type sets how Max-FTP should transfer the file type. ASCII is for transferring Text files, and stands for American Standard Code for International Interchange. Binary is for any file that isn't plain text, such as Executables and Pictures.
The application property is so you can set what application you want to use when you open a file of the given type in Max-FTP. By clicking the Use Windows Default, Max-FTP will use the default windows application for the given file type. The little picture of a folder is a browse button so you can find an application easier.