How to control a seven-segment display with 4 digits?
Get a power source (5 .. 12V DC) and connect a 1k resistor to the +. With the two wires, connected to gound and the (other side of) the resistor you can probe various pin combinations. When you have a combination that lights up a segment, start trying other pins while holding one pin fixed.

These are LED displays, so they are direction sensitive. In most cases one side of all segments of one digit are bundled together, and the other sides of all same-position segments of all digits are also bundled. How the two points are wired varies. Check any LED display datasheet for an example, for instance this one :



Using a display like this requires either a chip that is designed for this purpose or an appropriately programmed micro controller.