What is Quickly?
Basically it's a command line based tool for building applications. So go ahead and open a terminal. Now it will be useful if you're familiar with the Python programming language. If you're not then there are tones of on-line resources to help you learn.
How to create a new application:
Type: quickly create ubuntu-application mybrowser
Quickly will create a directory with the same name as your application containing all it's files.
How to edit your application:
In the applications directory type: quickly edit
How to edit the GUI:
In the applications directory type: quickly design
How to run your application:
In the applications directory type: quickly run
How to package your application:
In the applications directory type: quickly package
You might also want to watch this video. It will take you through the development of a very basic web browser application.