Any course of your academics.

Like machine design, mechanics of solids, fluid mechanics, engineering mechanics etc., 

You can attend the classes with the frequency you are comfortable with and get a demo if needed for better clarity

People who are going for gate classes can also take this class as I have done my masters via gate in NITW. So have some knowledge on these subjects of academics or gate whatever. 

Class can be hourly or half day as per convenience and requirement. Online is also available. So basically mechanical engineering is the stream where you have to understand before solving something which needs thorough thought process and analysis skills so that kind of analysis power should be developed with learning and understanding the topics on a broader mote rather than just solving them numerically or on formula based so make an understanding of each and every task we perform.