4-Digit 7-Segment Displays are tricky to use in circuits. These instructions will walk you through the process to get your your display corretly attached to your Arduino so you can get it coded and running.
Once your display is correctly wired, you can use this code to get it running. Then play with the code to see how to change the numbers that change on the display. Change the length of the delay in the code to a very small number to see how to display more than one number at a time.