Navigate to Siteworx >> Hosting features >> Domains >> SSL
First you need to generate the Private KEY. Click on Setup Private Key
This key is very important and should be kept private. it will be used with the certificate to encrypt your site's data.

If you do not already have the KEY, then click generate to create a new KEY.

Select 2048 bits as that is current standard, click Generate button. You'll be returned to the main SSL page.
The next step is to create the certificate signing request. This will be used to request the actual certificate from certificate authority like Geotrust.
Click Setup CSR

In the new page enter Country, state and other details.
Note: You can select domain.com or www.domain.com as the common name. Even if you do not use www - its recommended to include www for the SSL. SSL will work for both www and without.
Once data is entered click Generate button.
Note: If you already have a CSR then import using the option at the bottom at the end.

Then click View CSR option in the SSL page . Copy the CSR (you can verify it at https://www.sslshopper.com/csr-decoder.html) and submit it to the SSL provider.
You will use this CSR to provide to Geotrust when requesting certificate. Geotrust will use this to issue the certificate.

Once you get the SSL certificate, click “Set up SSL Certificate” option to complete the set up

Paste the certificate provided by the vendor in the test field and Click install
Once installed, you will be returned to the SSL main page. On this page you'll see your certificate details and the vender information if it worked correctly.
Finally, you do have option when setting up the certificate to use Self Signed Certificate. You would use the Generate button instead of pasting in a certificate from the certificate authority.
Please note: SHA-256 is current standard. SHA-1 is no longer considered secure.
You may wish to add the bundle certificate by installing it under the SSL Chain Certificate.
RapidSSL Intermediate certificate: https://knowledge.rapidssl.com/support/ssl-certificate-support/index?page=content&actp=CROSSLINK&id=SO26459
Other Geotrust like quickSSL or True Business intermediate certificates (select ones under RSA SHA-2 group): https://knowledge.geotrust.com/support/knowledge-base/index?page=content&id=INFO1421