Need to set ILS freq when using FMC?

Having fun with the 737 that I just purchased! I downloaded my first flight plan from SimBrief and figured out how to get the FMC to load it. I am new to this FMC stuff and flight plans but I got enough of it to work that the plane actually flew the route (KORD => KJFK). I guessed at an approach, ILS 4R.

When I got near JFK the plane did everything once I reset the MCP Altitude. The plane came in for a perfectly aligned landing on 04R. The only problem is I guess I did something wrong and the plane was going to fly over the runway at like 50'. I am sure it was pilot error. (I have only gone through Tutorial 1 once).

But my question is the plane came in great on 4R even though I never touched or programed the ILS freq for 4R.

So when using an approach in the FMC does one have to enter the ILS of the runway? DId I get lucky or was it somehow set by something else or maybe did I select a visual on 4R?. I don't know. Thanks for any help.

JC