How do you convert cyclohexane to chair conformation?
I can only urge you to get a set of molecular models. Your chemistry teacher will be glad to give you a set.
A six-membered ring with 6 tetrahedra naturally assumes a chair conformation as the conformation of lowest energy, which minimizes trans-annular interactions. Knowing this is no substitute for getting a set of models and having a play with them. Now, not only do you have to be able to recognize the conformations, you also have to able to translate that 3D geometry onto the 2D printed page. This is certainly non-trivial.