First, you will need to create a Mine schematic. For tutorial purposes, I am using a sand block. You do not need to worry about the bedrock, the plugin calculates the dimensions of the bedrock so you do not need to worry about that! This leaves you with more time to build your creation than worrying about dimensions!

After you saved your schematic. Run "/PrisonCore Schematic {Schematic_Name}". So, for me. I would run "/Prisoncore Schematic test"

After you run the command, you will see a lot of text appear. It should look somewhat like this for your first time. If it displays "Could not find file" with the directory, that means you have not saved your schematic, or have used the wrong name. To debug, open your plugins file, and go through the directory to see what is there (or isn't there). 

To set the Mine Schematic, type "/admin mine setSchematic  {Schematic_Name}". This should come with either a message saying you have done it, or an error has occurred. The error message will display the file it is trying to grab, but cannot if it does not exist. This is CASE-SENSITIVE

Do not reboot just yet!

To set the world, tp to it with "/mvtp {World-Name}" and use "/admin mine setWorld"

Now you can reboot the server with "/reboot"

This is the final result! After some tweaking with your configs, this can become an outcome. This is just a grass island, but it's better than air! You can add more detail, and become creative with your island. Make the center bigger with mountains on the edge so the user gets closer with each rank? Or gets higher until they reach the top of the glass pillar with same width each time?

The fun bit now, configs. Here, will be the values for your mine. Goto /Prison-Core/config.yml and then go through to Type - Private_Mine. First thing you will see if the Schematic name. Enter the name from the command into there. Second is the world, This will generate in the world you set it as. Like "Mines", "Plots" etc. I'm keeping mine as World. For now, keep everything else the same. 

An easier way to enter a world, is to tp to the world. And type "/admin mine setWorld" - This will automatically set the world for you with no hassle.