Hi! And welcome!
Are you using the utiLITI which is the 2D graphic editor for LITIengine or are you intending to do everything by code? Both ways are possible but knowing which one you're using can help us help you.
Do you get an error message?
What is the code you wrote that is supposed to load resources and the sprite of the character?
Did you call super(<name_of_sprite>) in the constructor? Have you forgotten to call super() somewhere else?
Seeing your code, or part of it, will make it easier to solve the problem.
In the meantime, please have a look through this demo made with LITIengine which serves as basic introduction on how to use LITIengine: https://github.com/gurkenlabs/litiengine-gurk-nukem (make sure to look at the names of the sprite files).
Here, you can find some documentation that might help: https://docs.litiengine.com/ . Just keep in mind that the docs aren't fully completed yet.