And the actual solution to your question:
cp -v /home/username/* /home/otheruser
Is one way of doing it. This will copy files only however, and not work recursively to copy sub-directories: to do that add the 'R' option (recursive) to the copy command (cp -Rv). The 'v' means verbose, in other words the actions of copy are reported back to you, rather than you seeing just nothing, and left wondering what's happening.
If the manual is too much of a nerd-literate assault to the brain, try searching a relevant 'howto' in a search engine ('howto cp'), or ask back here. Welcome and good luck!