Assuming the remote machine has SSH successfully installed and working then it is a simple case:
rsync -v -u -a --delete --rsh=ssh --stats firstname.lastname@example.org:/home/username/remotefile.txt
This will copy files from /home/username/remotefile.txt on the machine at 192.168.0.100
to copy files to that same machine then the command syntax is as follows:
rsync -v -u -a --delete --rsh=ssh --stats localfile.txt email@example.com:/home/username/
I will do a more in depth backup write up using rsync soon.