When you get Internet through your local cable TV company, you often also get cable television at the same time. One of the benefits of these bundled packages besides the cost is that you only need one cable to come into your house for both TV and the Internet. Coaxial cables, which is what cable providers use in your house, can carry a lot of bandwidth and are able to carry TV and Internet. So you can easily split the signal for both purposes.
Connect a short cable to the wall outlet with the coaxial input. This is where the cable connection in your house is. Connect a cable splitter at the end of the cable.
Take a second cable and connect it to the other end of the splitter where there are two cable connections. Connect the other end of that cable to your TV input.
Use a third cable to connect to the other open connection on the splitter. Connect the end of that cable to your cable modem. You will have to set up the cable modem as normal. You may need a cable company employee to help you with the cable modem settings if this is the first time you are setting up the cable modem.
It may be illegal or against your agreement to use your Internet connection to watch cable TV if you have not paid for the TV service.