In this article you will see how to upload a file in the library using the REST API and jQuery.
Develop the project using the following method in the NAPA Tool.
On your Developer Site, open the "Napa" Office 365 Development Tools and then choose Add New Project.
Prerequisites
The following are important steps to be done before creating the app.
Specify the permissions that your app needs as in the following.
Choose the Properties button at the bottom of the page.
Default ASPX
Publish the App and click the Trust it Button.
Output
File uploaded successfully in Document Library.
Reference: MSDN
I hope you liked this article.
SharePoint 2013 Administration Essentials