if you want apply mod on all user you can edit the file /etc/profile adding the path of mysql
PATH="/bin:/sbin:/usr/bin:/usr/sbin"
become
PATH="/bin:/sbin:/usr/bin:/usr/sbin:/Library/MySQL/bin"
you must have root permission (use sudo)
otherwise you can insert in you profile, from your terminal:
echo export PATH=\$PATH:/Library/MySQL/bin > .tcshrc