How to swap a series outlet with smart outlet
If the little copper tabs between the screw terminals are intact, on both sides of the receptacle.  It's as easy as using twist-on wire connectors (or other approved device), to "pigtail" the existing wires.  That will leave you with a single wire, to connect to each side of the new device.

To create a pigtail.  Start by turning off the power, and verifying that it's off.  Remove the two white wires, and combine them with an additional length of same sized white wire, using a twist-on wire connector.  Do the same with the black wires.  

Now you'll have one white and one black wire, that you can connect to the new receptacle.