Appending the certificate can be done in many ways. Here is an example of one method that may work for you though we recommend managing the procedure in accordance with your organization's policies and procedures.
First move a copy of the LUA certificate to the Linux machine.
from the /etc/symantec/sep/ directory:
cp sepfl.pem sepfl.pem.old
cat sepfl.pem luacrt.crt > sepfl.pem
Where luacrt.crt is the directory and name of the LUA certificate.
cat sepfl.pem /tmp/luacrt.crt > sepfl.pem
You can confirm that the LUA certificate is added to the sepfl.pem file by using the diff command.
diff --normal sepfl.pem sepfl.pem.old
The difference should be the content of the LUA certificate.
Once this is done you can restart the smcd daemon or reboot the machine and confirm if definitions begin to update from the LUA using HTTPS.