Cable TV, TV antenna signals and other video signals are carried on coaxial cable. If you need to feed a TV signal that is being carried on coaxial cable to more than one device, you need to split the cable. You can purchase a device called a coaxial cable splitter. The splitter allows you to connect two coaxial cables to a single coaxial cable. Thus, you can connect the signal source to two video devices, such as two TVs, two VCRs, an analogue to digital converter box and a VCR, or a TV and a VCR.
Connect the original coaxial cable to the input of the coaxial cable splitter device. The input is usually the connector that is the only one on one side of the splitter. Connect the cable by inserting the centre wire into the centre hole and screwing the outer part of the connector onto the splitter connector.
Attach one of the extra coaxial cables to one of the splitter output connectors. It doesn't matter which output connector you attach it to. Connect the other end of that cable to one of your video devices.
Connect the other extra coaxial cable to the other splitter output connector. Connect the other end of that cable to your other video device.
You can purchase cable splitters with more than two outputs. If you need a single cable to feed multiple devices, purchase a splitter with enough output connectors.
Don't split the cable more than three times or it will seriously degrade the signal. Don't buy low quality cable splitters. They will seriously degrade the signal. Coaxial cable splitters split a signal source into two destinations. You cannot use a splitter to combine two signals into one. For example, you cannot use a splitter to attach two antennas to a single TV.