1 - Open 'App Store'.
2 - Select 'Updates' section.
3 - In case a higher version is available, it will be displayed inside 'Updates' section.
4 - Press 'Update' button and follow the indications. The update process will take a few minutes.
5 - Once finished, you will be able to start 'TwoNav' normally.
Note: If no versions are available it means that you have the latest version installed on your iPhone/iPad device.