Read this example in NS3:

https://www.nsnam.org/doxygen/basic-energy-model-test_8cc_source.html

Thank you

There are many tutorials that explained the node configurations in NS-3, I advise you to read the following:

1) https://www.nsnam.org/docs/manual/html/attributes.html

2) https://www.nsnam.org/docs/tutorial/html/building-topologies.html

I have read the tutorials of ns3 but i wanted to set the computing power to see the processing delay of packets.

But i have set the processing power and computed the processing delay using the Schedule method.

how can ns3 used to simulate UAV

There is a 3D mobility model in ns3 to set the velocity, pitch and direction of the nodes. You can use it to create the UAVs and form a network.

There is also an energy model to install the energy source on nodes and set their initial energy.