A DSL modem enables a computer to connect to the Internet. A telephone line must be plugged into the DSL modem in order to send and receive online signals. To convert a phone jack into an Ethernet jack that can be connected to a computer, install a DSL modem using the telephone jack in your home. A few supplies from an electronics shop are needed.
Place the DSL modem next to the computer that will be used to access the Internet. Insert the DSL's power supply AC plug into a wall outlet. Plug the power supply's power port cable into the AC port on the back of the modem.
Insert the modular plug at one end of a modular telephone cord into the modular socket on the telephone jack; the jack most likely is on a plate at the bottom of the wall, up against the baseboard. Insert the modular plug at the other end of the cord into the "DSL"-labeled modular socket on the back of the modem.
Insert the Ethernet plug at one end of an Ethernet cable into the "Ethernet"- or "Network"-labeled socket on the back of the modem; the tab on the Ethernet plug must be lined up with the slot on the top or bottom edge of the socket if the two are to connect properly.
Insert the Ethernet plug at the other end of the Ethernet cable into the "Ethernet"- or "Network"-labeled socket on the back of computer -- again lining up the tab on the Ethernet plug with the slot in the computer's socket.