Renew a certificate with Citrix Access Essentials

1. Launch the "Quick Start" tool
2. In the "Setup" tab
   click on "External Access" 
   then click on "Manage External Access"
   Click Next.
3. Select "Direct to this server" to access the server from the Internet.
   Click Next.
   If you want to renew your certificate without overwriting the existing one, on some Citrix A.E. version, you will have to click on "Create New Certificate Request - CSR" to launch the assistant. Then click Next.
4. CN: Enter the public FQDN of the server (example: citrix.organization.com).
   Of course, this DNS has to be working!
   Click Next.
5. O: Enter the official name of your organization
6. OU:Organization Unit: We advise not to fill in this field or to enter a generic term such as "IT Department".
   Click Next.
7. Enter the geographical information of your organization headquarters:
   L: The city, in uppercase
   ST: The state, in uppercase
   C: The 2 letter code of your country, FR for France
   Click Next.
8. Select "Manually submit the certificate request to a Certificate Authority"  
   ann click Next.
9. Indicate the name and the path to the temporary CSR file. Click Next.
10. Click Finish to generate the file.
11. Open the file in a notepad and copy/paste its content in our order form.
12. Go to your certificate status page (you will find the URL the delivery e-mail) and click the renew button. Paste the CSR in the order form
    if you cannot find your status page, click here

To generate a first CSR on Citrix Access Essentials (CAE): follow these instructions.

See the official guide as well (page 48 of the PDF):
Citrix Access Essentials Administrator's Guide
French version: Guide de l'administrateur Citrix Access Essentials