Install your Trustwave SSL Certificate
Click “System Configuration” in the navigation bar and click “ACS Certificate Setup”. Click “Install ACS Certificate” and choose the “Read certificate from file” option. Then provide the full path and filename of the .cer file which was e-mailed to you by Trustwave. Also, provide the full path and filename to the private key which you generated while making the CSR. The password for that private key will also need to be entered on that page.
When you click submit, your new certificate will be installed.