1) buy a length of telephone cable long enough to get from demark to modem location and a phone jack to mount at modem location
2) pull wire from demark to modem jack location
3) at demark, attach red wire from cable to red screw and green wire to green screw.
4) at modem jack, attach red wire to red screw and green wire to green screw.
5) plug modem into jack.
6) at any other phone equipment on same phone number, unplug phone and insert filter between phone and jack.