To add a client certificate in iOS, you will need to have the .pfx file on your desktop.
- Plug in your device to your computer
- Open iTunes and click on your device
- Click the Apps tab
- Select Touchdown for iOS on the left hand side Apps menu
- Tap the Add button under the Touchdown documents menu
- Find and select the .pfx provided by your IT team
- Click open
- Return to your device and configure Touchdown using your newly added client certificate.