Sorry, you need to be logged to update the MIB.
Alternatively, you can send the mib.xml file generated by the following command to Contacts.
% echo "<!---" >> mib.xml ; nsysctl -e kern.osrelease kern.osreldate >> mib.xml ; echo "-->" >> mib.xml ; nsysctl --libxo=xml,pretty -r MIB -DNkISa >> mib.xml