I need serious help.

[buran]

Well, as an intermediate java programmer what do you understand by 'user input'? seriously...
it's not possible to say it more clear -

Ask the user to input the file names of both files, and use the try-except construct when you open each in your program

both files being input file and output file. Regarding try-except - you need to handle situations when user input is incorrect like non-existing file...