If you are interested in designing interfaces, or learning about the development of websites and apps - for all varieties of platforms - I would suggest downloading Justinmind. The tool is relatively straightforward and the more you use it, the easier to understand. There are also tutorials on the mighty YouTube which can be of use in times of confusion; there is also the "help" tool on the software itself.
I have started playing with the mobile app templates (iPhone 6) and will publish that one when it is ready (and when I figure out the best way to post on the site). So look forward to that!
-DEBP