How introduce plugins?

i have plugins in libexec subdirectory of nagios directory.
do i add any things to config files in etc/ to tell nagios where the plugins are ?
in addition how can i use plugins in services.cfg ?
coz i see the plugins are run from command line manually but i want to have them in check_command option in services config file .

Please read the docs from start to finish one more time.
The location of the resource file is defined in the main config file. … ource_file

The resource file is used to store macro’s.
If you look at the checkcommands.cfg file, you will see that all checks start like this…
command_line $USER1$/somecheck
$USER1$ is defined in the resource.cfg as /usr/local/nagios/libexec
All plugins are located in that directory.
So check these and make sure they are correct, then config your services and hosts.cfg files, and bam, you are good to go.

Again, you appear to have skimmed over the docs much to quickly. It would help if you went through them, line by line, and understand each and every one, so that you can grasp the entire concept more easily and make nagios work it’s tail off for you.