Well sparkfun/ada/grove etc who make these little modules available to hobbyists all include sample code and project to work with them. Granted some of them may be “arduino examples” but in many cases not much will change, apart from some pin names for any buttons etc. However here is a thread Adafruit Led Matrix 8x8 that has several examples linked in it. Any example with an LCD in it will show you how to write to one, the only bit that might change is the initiaisation/setup depending on its address and if it is serial or not.
There are also plenty more in the projects section as well as examples included with the libraries that control the displays. As a general rule the libraries tend to be written in “proper” C++ so they use concepts like objects, inheritance and other things that you could also read about on the side so you can follow how they work. If you’ve ever used something like C#, Java,PHP or Python (to name but a few) you will have met these before.