How to Save Site As Template (stp file)
Go to "/_layouts/savetmpl.aspx" in your current site, Now you will see the option to save your current site as template. (screenshot given below)
Enter the stp file name and check the checkbox "Include Content" if you want to include the all content (lists, libraries,etc) from the site current site.
Note: If your Publishing Feature is not turned on you will see the "save site as template" option under SiteSettings -> LookAndFeel section, the above scenario will apply only when the Publishing Feature is turned off.
