Here is the link to the Panda3D website: https://www.panda3d.org/
The documentation is here: https://www.panda3d.org/documentation.php
However, I recommend that you heavily use the manual: https://www.panda3d.org/manual/index.php/Main_Page
If you take a look at the manual, you'll be able to tell very quickly that this indeed is a _huge_ module. We cover a few of the commonly used features in 112 in the Basic Tutorial.
All of the things we cover here are covered in the manual, which is your best friend, but your best friend is a little difficult, so here we are.
Also, here is the Wikipedia page on Panda3D: https://en.wikipedia.org/wiki/Panda3D
It's not the most useful, but alas.
Note on Running Panda3D
Panda3D is not an application, despite it sort of seeming like it when you download it. You can't _open_ it and use it. However, Panda3D does require you to run a version of python called ppython. This version of python comes with Panda3D, so don't worry about downloading it. However, you'll need to tweak your settings/run it out of the terminal. If you're not familiar with the terminal, here is a terminal tutorial for you, if you want to familiarize yourself with it. Later, in the Installation section, we demonstrate a way for you to set up a Sublime command to run Panda3D. However, we still recommend that you familiarize yourself with the terminal, as you might need it to install Panda3D.
Consider other options
Think about your project. A lot of people try to use Panda3D because they want 3D graphics, but in many cases, the projects don't fit the module. Panda3D does not let you generate objects. They have to be imported. Panda3D can be difficult to use, tricky, and oftentimes frustrating. Also, Blender is sometimes hard to use, and more importantly, another thing you need to spend time to learn how to use. There are other ways to get 3D graphics without using Panda3D - don't choose Pand3D if it doesn't match what you need for your project.
You can choose VPython, a much less powerful engine, but lets you generate primitive shapes. Vpython is more ideal for projects that require less complex shapes and less animation - for example, if you were making a project that displayed molecules or a Rubik's cube, VPython can definitely handle spheres, cylinders, and cubes, and using Panda3D might be overkill.
Another option is to use a 2D graphics package (tkinter is fine) and instead, draw some 3D objects, if your objects aren't super complicated. This way, you don't even have to learn a new module! The trade off is that you'll need to do more math. However, you can still get some really cool projects this way. Using a 2D graphics package, you can import 3D pictures as well.
Consider carefully. With that being said, Panda3D is actually a really versatile and comprehensive engine, and if your project idea fits with the module, it does a wonderful job (and looks super cool).