Step 2: Install the Intermediate CA Certificate
Open the Cisco ASDM, under the Remote Access VPN window pane > Configuration > Certificate Management, and click CA Certificates.
Click the Add button.
Assign a Trustpoint Name to the Intermediate CA certificate (i.e. IntermediateCA.crt, as described in Step 1), select the Install from a file: radio button and browse to IntermediateCA.crt certificate file. Click Install Certificate.
The certificate is listed within the Trustpoint Name you assigned.
Locate the SSL certificate (i.e. ssl_certificate.crt, as described in Step 1) you downloaded on the server.
Under Remote Access VPN, expand Certificate Management > Identity Certificates.
Select the identity you created for the certificate signing request (CSR) with the Expiry Date shown as pending and click Install
Select the SSL certificate file (i.e. ssl_certificate.crt, as described in Step 1) and click Install Certificate. Once installed the Expiry Date will no longer show 'Pending.'
The SSL certificate now needs to be enabled. On the lower left, click Advanced > SSL Settings. Select the interface you want SSL enabled for and click Edit.
On the next screen, click the drop-down menu and for Primary Enrolled Certificate select your certificate. Click OK.
The ADSM will then show your certificate details under trustpoint.
If you are unable to use these instructions for your server, Symantec recommends that you contact either the vendor of your software or an organization that supports Cisco ASA 5520.
Step 3: Verify certificate installation
For more information, see Cisco Support website.