Actually, you have to import the contacts from the "People" app that HTC pre-installs.
From the Home screen, tap applications, then People.
Press the menu button at the bottom of the phone (it looks like a series of lines stacked on each other) and then tap Import/Export > Import from SIM card.
If you have Google or Exchange ActiveSync accounts set up on HTC Sensation, tap the type for the imported contacts.
Do one of the following:
Tap one or more SIM contacts you want to import.
To import all contacts, press , and then tap Select all.