Using a 4-1 multiplexer
So the part you have is an CMOS dual one-of-four digital multiplexer.

With CMOS logic circuits you should tie every single one of the inputs on the chip to a valid logic level, either directly to a supply line or through a resistor.
The outputs can go somewhere (maybe a logic input or a resistor + LED, or even both if you keep the LED current low) or they can be left open.
An easy way to do that when you are playing with it on a solderless breadboard is to have a pullup or pulldown resistor such as 10K to a supply rail and use a switch to the opposite rail to control the input.



simulate this circuit &ndash; Schematic created using CircuitLab
The resistors R2 R3 are optional if you don't use a switch. R1 is required, otherwise SW1 would short out the power supply when closed. In the latter circuit the input is high with SW1 open and low with SW1 closed.