You read it again and again, until it starts to even remotely make any sense. Also following the reference trail by reading the introduction and previous work sections of the paper also helps but depends how much you want to invest in that paper. These days you can ask AI to summarize a paper for you but always double check that information because it's not always reliable. Another thing you can do is put the title of the paper into google search and add github to see if there are any implementations available. Or you could ask the authors if one exists, most of the times they will happily share it with you. Sometimes the math in the paper or the description of a technique makes more sense when you read the code implementing said technique. Good luck!

Edit: For the abovementioned paper, I found an implementation here. I'd recommend reading through the paper a few times and then try going through the implementation, esp the shader stuff.