Configuring hosts with different platform (windows, linux)

Under windows.cfg

Open the file using a text editor and add below definition -:

Opening Nagios.cfg file under - /usr/local/nagios/etc

uncommenting below line, and save -:

cfg_file = /usr/local/nagios/etc/objects/windows.cfg 
Verifying Nagios config. 
# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Output -: 

Added hosts will get displayed on Nagios dashboard - 

Same way it's needed to be done for Linux machines.