To delete any application from a tablet or a smartphone, then also RistoManager, you must first access the Settings, which are accessed by clicking the center of the lower bar that leads to the list of all applications, from which then choose the icon with Settings ;

you will get the complete list of the currently installed applications (on smartphones it may happen that it does not appear in the list, in that case just move to All) and scroll to RistoManager:

you will come to the options to manage the application, among which you will have Uninstall; by clicking on that button, you will delete the app from the tablet, while to delete

all data (including login data such as password) of RistoManager.