How can I log simulator time in ForeFlight Logbook?

Prior to creating an entry for the simulated flight, you will need to create a logbook aircraft instance for the simulator. You can do this by navigating to More > Logbook > Aircraft in ForeFlight Mobile and then tap on the + symbol at the top right. Enter the details of the simulator and, once that is complete, you will then create the flight entry and reference theFull Flight Simulator (FFS), Flight Training Device (FTD), or an Aviation Training Device (ATD) in the Aircraft field.

In order for Approaches and/or Holds to count towards currency in Currency Summary, you will need to set the Category/Class of the FFS, FTD, or ATD in Logbook > Aircraft.