I need any steps or videos explain how to add device template in site24x7 dashboard because i can't find our router in templates.
If there is no preset template corresponding to your router, you can create a custom device template.
Please refer to this help doc for adding, editing, and associating device templates.
If you wish to add custom performance counters, this doc can be helpful.
You can also refer to the video below:
Hope this helps.