How to install a CA in Linux Hosting Control panel
To install a CA (Or Intermediate Certificate, or CA Bundle), please follow the steps below:
1 - Obtain certificate from CA. (This tool will give a download for it at the bottom https://ssltools.websecurity.symantec.com/checker/views/certCheck.jsp)
2 - Login to Plesk.
A - Click on domain name.
B - Click on SSL Certificates.
C - Click on the certificate.
D - Paste in Certificate where it asks for CA certificate.
E - Click on Send Text.
3 - Wait 5+ minutes to take effect.
**** To use a CA bundle provided by GeoTrust with SHA-2 (https://knowledge.rapidssl.com/support/ssl-certificate-support/index?page=content&actp=CROSSLINK&id=SO26457), you may need to alter the bundle by removing the SHA1 intermediate CA certificate from the bundle.
Once you have done this, use this altered CA bundle when installing your Intermediate CA, bearing in mind that this altered bundle may not be compatible with older operating system and browsers.