SharePoint 2013 has a new UI and a new way to Create Sites or Sub-sites.The option is now located in View all Site Contents instead of
the settings menu.
Lets look at the Steps to create a site and sub-site:
Step1:Log into your SharePoint 2013 site.
Step2: Click on Site Settings Wheel in the upper right corner of you site and select “Site Contents” from the drop-down menu.
Step3:At the bottom of the page, click on new sub-site under the Sub-sites header.
Step4:Enter the Title and Description of your new sub-site, choose the URL for it and select a template for this sub-site
Step5:Select the necessary permission and navigation settings and click Create.
Step6:Now you can see your newly created sub-site.
Step by Step process to create a Provider Hosted App in SharePoint 2013..