Apple and Android apps are forms of Software.
Noodletools has "Software" as an option in its list of choices under Electronic/Online (Exclusively) in all three formats (MLA, APA, and Chicago).
Since you are citing a Mobile App, once in the Software form, make sure to switch the top tab to "Mobile App."
From there, you should be able to fill out the form with the requested information as best as possible with the information provided through the app itself and the app store where the item was purchased. Remember that clicking on a box to fill out will provide you with a definition that field.
For more help, check the links below and/or stop by the library to speak with Ms. Covintree.