i am new user to unix. just started today. i have a task on my hand. please help me out.this may be the most simplest question to you guys.

i have to upload a file ABC in some directory for example lib..i am already at the promt where i want to load that directory

now my destination directory i.e. the directory i want to copy is in home/username/Desktop/XYZ

i try giving this command:
$ cp /home/username/Desktop/XYZ .

but it doesnt work ...please help...
thank you