I have iso image of windows 7. How can i create windows vagrant box using this iso image.
I tried "vagrant box add name fileLocation of iso". But box wasn't created.
Vagrant works with box not OS ISO
You can read more on box at https://docs.vagrantup.com/v2/boxes.html but basically Boxes are the package format for Vagrant environments. A box can be used by anyone on any platform that Vagrant supports to bring up an identical working environment.
The easiest to start with is to download an existing box (.box file) both https://app.vagrantup.com/boxes/search and http://www.vagrantbox.es are good resources to find a box that should match your need.
If really you want to start with the ISO and build your own box (this is more advanced topic, I would only recommend for specific usage), you would need to look at the packer tool (https://www.packer.io) and getting existing templates for your target OS (like https://github.com/joefitzgerald/packer-windows for windows box)