The smartphone must support it (most newer HTC models do) and the provider (Verizon) must support it. Verizon has drug its feet in the past, trying to get its customers to pay for their separate PC services, but has made it an option for owners of select smartphone models. When you ask them about availability, specifically use the term "tethering" and make it clear you're prepared to walk if they push additional fees.

Hope this helps,