Looks like you’re on the right track and that’s a very decent high quality lock and can do all you’re looking to do.
Unfortunately, for now, SmartThings requires all custom apps and devices to be installed manually hence you see code instead of an install link. You should download the SmartThings Classic App from the Apple App Store or Google Play Store to install custom apps (once installed you can go back to the new ST app).
Seeing code can look a little daunting at first, but it’s fairly easy (most a copy paste job) to install a SmartApp or a Device Handler. We’ve put a step by step instruction guideline in place to assist first time users.
Here are the instruction to install a SmartApp (in your case Lock User Management) http://www.rboyapps.com/InstallSA.htm