iPWMinder is a file-based application. All the passwords you create and manage are stored in a Repository Files (with a .pwm extension). Like any other important data, you should make sure you backup your data to help prevent loss.
If you are using iPWMinder with Dropbox, then Dropbox automatically keeps backups (a history) every time the file is saved so you don't really need to do anything to back up your Repository files.
If you are using iPWMinder with a Local Repository file (i.e. file is stored on Device), then you should regularly back up this file, by copying it to your Desktop computer. Copying files from your iOS device to your Desktop computer is similar to copying files from your Desktop computer to your device (see article on How To Copy an existing .pwm file to iPWMinder, using iTunes), but instead of clicking Add..., you select the file and click Save...
In addition to backing up the iPWMinder Repository file, you should also regularly backup your entire device. For instructions on how to backup your device see Apple's article: iOS: How to back up your iPhone, iPad, and iPod touch.
