You must be logged in as root. On Fedora, useradd and adduser are synonymous.

# Use this command to add an account (a user, aka login).
# Create user mst3k, and create /home/mst3k and populate it.
# Create matching group also (apparently implicit for Red Hat user add).

useradd -m mst3k


# Set the new uid (and gid) to 500. Use this if you are creating an 
# account for a user who has an exisiting account on another machine 
# and you want the uid/gid to match. Matching helps solve ownership issues
# when moving files between different machines.

useradd -m -u 500 mst3k