There are several ways to install applications on Android: the simplest — and safest — method is to open the Google Play Store (or pre-installed alternative stores) and search for apps there. Finally, one can resort to manually installing APK files and their variants, which are the packages containing all the application's files.
You've started storing important data on your computer and want to keep it away from prying eyes without setting up complex locks that could slow down your work.
Excel, the renowned spreadsheet management software provided by Microsoft, includes an impressive number of features that allow for extremely flexible data manipulation.