This is very hard. I whink they should take this easy to us. I will post the problems I have facing with this in another thread.
To install a Wildcard SSL, first, you generate a CSR. You need to use *.domain.com in CN. The file will be generated with "*." in name, this is your first problem, because it is not recognized by panel.
Login in SSH and rename file "*.domain.com.csr" to just "domain.com.csr". Do the same with key file.
These files are located in "/etc/pki/tls/certs" and "/etc/pki/tls/private".
After this, get your CSR and order your certificate.
After you receive your certificate, you must paste the certificate in file "domain.com.cert" inside "/etc/pki/tls/certs". I don't remember if this file is created empty. If not, create yourself using panel file manager.
When you go to install your cert for your domain, the panel suggest the "*.domain.com" as domain, you need use only "domain.com" as domain, otherwise, will not work. This is the second problem, because the panel use the domain name you specify as file name.
When you go to install the certificate for other subdomains of your domain, the panel use a diferent file for each subdomain, but this certificate is a Wildcard, there is no sense to use diferent filenames for this, just specify other domain and your are ok.
In this case, you will need to copy the content of certificate file to this new created subdomain file, and for the bundle file too.
The bundle file must contain the certificate for your domain (the one you bought) and below the root certificate from your certificate provider.
This is a bit confusing.