I'll go out on a limb and say "how to build a robot". Its not something that most people can just do without any training, though there are no doubt plans online. You might want to learn the 3 rules of robotics,,, lol
Do research involving what tools and parts you will need. Possibly welding because that would be important during the process. Also, what kind of robot? What do you want your robot to do? Really think about what your robot is going to be used for and the different gripping or moving options. Then build on your ideas by doing plenty of research.