We bought a used 2016 Fusion SE with one key and no keyless entry code. How can I get the code to the keyles entry?

That code is somewhere in the vehicle. Sometimes it is under the center counsel, or in the trunk back deck.

Code is stored in the body module. Take to you local ford dealer for the code.

Check the owners manual on the back it could hold a card showing you your code as mine did after I was searching up ways to get it without paying ford the fee.

Use 2 sets of your keys. Insert first set into ignition and turn on (Do Not Start) Wait 5 seconds and turn off. Insert second set of your keys into ignition and turn on (again Do Not Start) wait 5 seconds; your code shows up in your instrument panel right away.