Unfortunately Smartthings made it very hard to get personal apps in to the app store in the app a while back. With that happening the best way to get it loaded is to find the app here and then log into the IDE yourself and publish the app. There are some good tutorials on this out there…
The IDE is at Smartthings IDE
You would go to the IDE, setup Github integration, and then publish the app and it’s components if any to your location.
You also need to ask if you are using the Classic Smartthings app or the new Smartthings app. To install community developed apps you need to use the classic app. Once they are installed in your location though you can manage them from the new app if you choose to use it.
I will do some searches for the tutorials and post them here.
Github integration with the IDE tutorial
Thread with many totorial or FAQ links for information about custom apps.