It goes to the air freight/cargo section. There are a number of companies that handle air freight, including Royal airport services, Gerry's etc. It will end up in their warehouse. The company that booked your cargo at the source will have a local agent in Pakistan. The local agent will call you when your cargo arrives at the warehouse. You need to bring your passport, cargo booking form etc., any thing that you were given at the time of booking the cargo.
The local agent will get you through the process of getting the cargo released. It will take a few hours, if you are lucky you could get it released the same day.
Customs will check your cargo and charge you for any dutiable items, you will also need to pay CAA charges and lastly pay the agent.
My brother booked some cargo from Australia, it was mostly used household stuff about 90KG in total. CAA was demanding Rs. 16,000 as charges for same day release. For next day release they were charging Rs. 9000. Funny how things work in Pakistan. We also had to pay Rs. 5000 to the agent, the custom officer went away empty handed since there was nothing dutiable in the cargo