I'm not sure which documentation you were referring to, or what words you didn't understand, but a Google Search came up with Waveshare's product page, from which I got to the wiki link.

I haven't used LVGL before, but from the content in the wiki link, they appear to have some support for LVGL in Python. Maybe start with the Getting Started section for MicroPython, and see if you can get the LVGL demo working using the corresponding section on the Wiki.

I wouldn't go and try to find solutions from somewhere other than Waveshare because it's their product, and they did say something about not installing generic firmware.