If Marxism-Leninism is a science, there must be some technical aspect. What are we supposed to do in the world? How do we do it? And how do we know if it's working?

Check out the book The Worldview and Philosophical Methodology of Marxism-Leninism it covers this in its intro:

The word “science,” and, by extension, “scientific” in Marxism-Leninism has spe- cific meaning. Friedrich Engels was the first to describe the philosophy which he devel- oped with Marx as “Scientific Socialism” in his book Socialism: Utopian and Scientific. However, it should be noted that the English phrase “scientific socialism” comes from Engels’ use of the German phrase “wissenschaftlich sozialismus.”

“Wissenschaft” is a word which can be directly translated as “knowledge craft” in German, and this word encompasses a much more broad and general concept than the word “science” as it’s usually used in English. In common usage, the word “science” in English has a relatively narrow definition, referring to systematically acquired, objective knowledge pertaining to a particular subject. But “wissenschaft” refers to a systematic pursuit of knowledge, research, theory, and understanding. “Wissenschaft” is used in any study that involves system- atic investigation. And so, “scientific socialism” is only an approximate translation of “wissenschaftlich sozialismus.” So, “scientific socialism” can be understood as a body of theory which analyzes and interprets the natural world to develop a body of knowl- edge, which must be constantly tested against reality, with the pursuit of changing the world to bring about socialism through the leadership of the proletariat.

The book focuses on, as it says on the tin, The Worldview and Philosophical Methodology of Marxism-Leninism. It wants you to understand the philosophical methodology behinds Marxism-Leninism. Its a translation of a Vietnamese college course on ML theory that is required study for all college students.

So you must strive to have a Marxist-Leninist Worldview (The whole of an individual’s or society’s opinions and conceptions about the world, about humans ourselves, and about life and the position of human beings in the world.) and to build that worldview within you requires reading theory. You want to test your worldview against objective reality often and regularly.