If you need to make a footnote, use the following example:

For those of you who need to perform a server-class
<footnote>
<para>
A server-class installation sets up a typical server
environment. Note, no graphical environment is 
installed during a server-class installation.
</para> 
</footnote> installation, refer to the <citetitle>Installation Guide</citetitle>.

The output:

For those of you who need to perform a server-class ^[2] installation, refer to the Installation Guide.