I'm learning to code, I would love to learn how to do something like ...
Is there a chance to see the source code?
If it's procedural generation of the dungeon what you're interested in, this tutorial might come in handy. Part 3, in particular, shows you how to create a basic dungeon generator that will produce something similar to this tool. Alternatively, I have some code here, made in Processing.
It's a programming environment with an unfortunate name, hehe. It makes googling a pain. It's very easy to draw stuff, you can find it here: https://processing.org/ The dungeon generation algorithm doesn't really require it though, it should possible to follow in whatever language you're using.