Write the rightsholder, which stands for either an individual or corporate author of the software, followed by year, title of the software, version number, description of form and from where you have got it.
Rightsholder. (year). Title of app (Version number) [Mobile application software]. Retrieved from https://xxx
Skyscape. (2013). Skyscape Medical Resources (Version 1.17.42) [Mobile application software]. Retrieved from https://itunes.apple.com
Note: Android apps should have similar address: https://play.google.com/store/apps