There are no specific intructions to replicating a prop. Tutorials on how other people had made their particualr prop are available here. Some may differ from others since many people will take a different approach to a certain prop. We will study them, follow given advice, or embellish on the information provided.
As suggested, select a prop you're interested in. Then assess your propmaking skills - what kind of tools do you use, are you artistic, can you sculpt, etc. What materials are you comfortable working with -wood, metals, plastics, resins, paper, etc.
There is a wealth of information available on this forum. Take the time to look though the threads that interest you and learn what others have done.
The most impressive thing among the people here is the creativity that they can come up with. I could be mean and suggeat an arts and crafts site would be better for you if you require instructions, but give yourself a chance to see what you can create.