If you do need to setup ssh login between your servers or between your personal machine and server, see this link:

http://www.thegeekstuff.com/2008/11/3-steps-to-perform-ssh-login-without-password-using-ssh-keygen-ssh-copy-id

For writing the usb image files, likes the one mentioned at ftp://ftp.freebsd.org/pub/FreeBSD/releases/amd64/amd64/ISO-IMAGES/10.3/,  to usb drives on a mac, see this link https://people.freebsd.org/~seanc/freebsd/create-memstick-osx/ .

The usb images are differentiated from the normal ISO files by the presence of “memstick” in the file name.

Cheers