If you delete the application, your Locker containers, that store the encrypted files and data will not be deleted - you would simply lose the access to reach them. Once the application is installed, you will be able to access the files again.
To uninstall the NordLocker application navigate to your Applications folder using Finder and locate the NordLocker application. Drag and drop the application icon into the Trash (at the end of the Dock) or right-click on the icon and choose the Move to Trash option in the pop-up menu.
Please note that the application will be permanently removed from your Mac the next time you or the Finder empties the Trash. If you decide you want to keep the app, get it back before emptying the Trash - select NordLocker in the Trash - File - Put Back.
Then download and install NordLocker here.