If you are trying to install an app to SharePoint 2013 RTM environment or to Office 365 then you might see the below error if you are trying to deploy the app to the site which is not developer site.
Error occurred in deployment step 'Install App for SharePoint': Side Loading of apps is not enabled on this site.
Solution:
Always the app should be published/deployed to the developer site (A site collection with the Developer Site Template). And from this developer site you can add the App to your SharePoint site.
Error occurred in deployment step 'Install App for SharePoint': Side Loading of apps is not enabled on this site.
Solution:
Always the app should be published/deployed to the developer site (A site collection with the Developer Site Template). And from this developer site you can add the App to your SharePoint site.