Step 1 When Sectigo returns the Identity Certificate to you, return to the Identity Certificates panel, select the pending certificate entry, and click the now active Install button.

Step 2 To assign the newly installed certificate for use with SSL VPN, navigate to the SSL Settings panel by SSL Settings hot link in the text under the list of certificates.

Step 3 In the SSL Settings panel, double-click the interface to be assigned to the certificate. the Edit SSL Certificate panel opens.

Step 4 In the Edit SSL Certificate panel, select the certificate from the Certificate: pull-down list and click OK.
Note that the selected Identity Certificate displays in the ID Certificate field to the right of the selected Interface field.

Step 5 Be sure to click the Apply button at the bottom of the SSL Settings panel to save the newly-installed certificate with the ASA configuration.

You will also have to install your Root and Intermediate Certificates. For details, see:

http://www.cisco.com/en/US/docs/security/asdm/6_1/user/guide/certs.html#wp1287101