Look at the back of the old switch near the terminals. All the terminals are lettered/numbered. The new switch has the same corresponding lettering/numbering for each terminal except that there are 2 terminals instead of a "splitter" for the one tandem wired terminal. Sorry can't remember the designation (lettering/numbering).
I will need the model number and manufacturer of the equipment you will be using this switch on to find a diagram. Please call our sales team with this information 1.888.388.6372. They can get you want you need.