The following procedure shows how to create a sub-site in SharePoint 2013.
Log into your SharePoint 2013 site.
Click on the "Settings" icon and choose "Site Contents" from the drop-down menu.
At the bottom of the page, click on "new subsite" under the "Subsites" header.
Enter the "Title" and "Description" of your new subsite, choose the URL for it and select a template for this subsite.
Select the necessary permission and navigation settings and click "Create."
Now you can see your newly created sub site.