If you already created a user and you want the user to be able to
<command>su
</command> to
<systemitem class="username">root
</systemitem>, you can log in as
<systemitem class="username">root
</systemitem> and edit the file
<filename>/etc/group
</filename>, adding
<systemitem class="username">jack
</systemitem> to the first line (the group
<systemitem class="groupname">wheel
</systemitem>). But first you need to practice
<citerefentry><refentrytitle>vi
</refentrytitle><manvolnum>1
</manvolnum></citerefentry>, the text editor—or use the simpler text editor,
<citerefentry><refentrytitle>ee
</refentrytitle><manvolnum>1
</manvolnum></citerefentry>, installed on recent versions of FreeBSD.