I cant use pcap.h include file. How can I do so? 
Errrr...
#include <pcap.h>
perhaps? If not, explain what the problem actually is before asking for help.
first check whether you have the packet capture library
and pcap.h available under /usr/include
else you cannot use it
If you have pcap.h in /usr/include type:
#include <pcap.h>
If you don't have pcap.h in /usr/include:
download it (but i can't help you to find it, I don't know where you can find it, ask it someone), save it in the directory of the source program that use pcap.h and in this source type:
#include pcap.h
Freddie
you dont have to copy it to some directory. If it exists somewhere on your file system and you know where then simply use the -I compiler flag when you do the compile, so lets c it is in /tmp, then you compile as
cc -o outfile sourcefiles -I/tmp
The advantage of this is that pcap may be using other .h files and if pcap is some package library then logically the other .h files should reside in the same directory as pcap and this referencing them will be easy. else if you manage to include pcap.h and pcap uses say nocap.h the you ll get an error that you cant find nocap. so using the -I flag would help resolve such recursive errors.
btw what is the pcap.h file
as i had mentioned earlier
its the important header file for packet capturing library routines
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Great! 
Freddie