There is lots of documentation on the internet about this subject, but this is meant to assist novices to get up and running asap. SAP has created a website (buildme) with sample apps that can be customised within the site. It can then be exported and used as a sample that can be edited.
Webide is SAP’s online editor where you can import your buildme app and then edit it. You will be required to register on the site before being able to import projects. This is only an editor and will need to be exported to SAP.
Eclipse can also be used to edit Fiori Apps. These apps will need to be deployed to your sap system as BSPs or executed from an IIS.