How will I change the beginning of the novel?

I'm sorry, this is a short-answer literature forum designed for "text based" questions. We are unable to answer questions regarding writing assignments. Look at the beginning of the story.... it's set in Holme's home. Possibly you could arrange the meeting between Holmes and Mortimer at a differrnt location. Possibly Holmes is already visiting Devonshire and meets Mortimer there, maybe, he's been called in to investigate. There are no lack of options in rewriting the story's beginning, though, I doubt any of us can do it as well as Doyle.