is there a documentation on how to do Physical inventory in NetSuite? I see the physical inventory worksheet, where you can see on hand and write the actual number but is there any other documentation other than that report/worksheet?

There is a ton of documentation in the RF-Smart knowledge base. There are also some great videos by them on the inventory process. I was able to do a complete physical inventory of my warehouse by following their documentation.

Unfortunately we don’t have RFSMART

Ah! bad assumption on my part. Sorry, I don't have a suggestion for you. good luck.