I already have the Ramblers Walk register App can I update or do I need to install the new Ramblers App?

If you have automatic updates on the app should update - you will know it has as the icon will be blue with the Ramblers R and have the word Ramblers 

If you do not have automatic updates turned on, or if you wish to do this manually

go to the Apple Store Click here to get it on the App Store 

or Play Store Click here to get it on Google Play 

Or search in the stores using 'Ramblers' and click on update.