Welcome to the forums! Look for a tuner card or USB stick and software that has "clear QAM" capability. Either will have an F-connector for hooking it up with the house cabling. Sellers include Hauppauge, SageTV and BeyondTV.
Do be aware that "clear QAM" service may be limited to your local broadcast channels (and at least on one case, only just analog versions of them). The FCC has decided to allow service providers to scramble all other services, so that they can be safeguarded from inadvertent reception by folks who haven't paid for those services.