In my simulation in NS3, I have some mobile nodes. So, I include mobility pattern of the mobile nodes from real-trace. What is the procedure I need to follow?
It depends mostly on the format of your trace file.
The simplest way would be if your trace was in (or could be easily exported to) legacy ns-2 trace format (tools like SUMO or Bonmotion usually allow you to generate traces in this format). In those cases the ns-3 API includes the ns3::Ns2MobilityHelper (std:.string filename) which allows you to import and set-up node mobility using the specified filename.
In other cases, you would need to create a custom mobility model including a parser for your trace file-format. This parser would be responsible of initializing your mobility model according to the contents of the file (for this kind of network it would usually be a WaypointMobilityModel and you would be adding the waypoints).