Admin Interface

How do i create an admin interface through webform.

I have an Excel sheet it contains some information(I created some tables in Database for this to interact with admin), it has to be updated their values at time to time when we update at admin. Please suggest me on this how do we interact. Moreover,where we should add the PHP snippets in webform ("Under the "Webform advanced settings", enter the snippet, including the tags"). I didnt found any text field to enter this snippets in my advanced settings.. Please guide me on this too........

Thanks u soo..... much