Hi Bhavna,
This is because if you open the wscript file under ns3-LEO-main, you see the line :
module = bld.create_ns3_module('leo', ['core','internet', 'propagation', 'stats', 'flow-monitor', 'applications', 'netanim']).
Then do .#/waf configure --enable-tests --enable-examples -d debug, from the ns3 directory and build again.
Do let us know in the group if it helped.
REgards,
Abhi