Please follow these instructions to install your SSL certificate on SonicWALL Aventail EX-1500:
Install your SSL Certificate
1. Once you received your SSL certificate by e-mail, please copy and paste it into a text file (with Notepad or Wordpad) and save the file with the .p7b extension. (Include the tags -----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----).
2. Launch Aventail AMC.
3. Go to SSL Settings. (Path: /console/configSSLCert.do)
4. Press the Import Certificate... button.
5. Select your .p7b file from step 1 and click OK.
Configure Aventail EX-1500 for Client Certificate Auth SSL
1. Configure LDAP Authentication. (Make sure before that users are able to authenticate using LDAP Username/Password before attempting to authenticate with a cert)
2. Fill in the different required fields.
3. In LDAP over SSL, check Use SSL to secure LDAP connection.
4. Press OK.
If you need further information, look at the official guide.