If your file(s) resides in another location. You can type the path like so. An Example:
mv ~/Documents/filename.txt ~/Documents/newfilename.txt
Or cd to the Documents folder and then use mv or cp
mv filename.txt newfilename.txt
Remember, mv works in two ways. It will move a file(s) to another location or rename the file(s).
Also, if your files have special characters, you'd need to use an escape character like '\' or wrap the filename in quotes.
this\ is\ a\ sample\ file.txt
"this is a sample file.txt"
In these two examples, the space is the special character.
You can also use TAB completion to fill the rest of the filename. Just type the first few letters of the filename and press TAB. If it's the only file that begins with those letters, TAB completion will fill the rest.If not, type the next letter and press TAB. Keep repeating until TAB completion fill the filename completely.
TAB completion can work on files, directories and directory paths.