According the Legend the Wall is built 8,000 years ago.
The Nights Watch is military order which holds and guards the Wall, the immense ice structure which separates the northern border of the Seven Kingdoms from the lands beyond.
The Nights Watch consists of three groups: the Rangers, who fight, defend the Wall and patrol the Haunted Forest; the Builders, who maintain the Wall and the castles; and the Stewards, who support and feed the members of the Watch.
Choose to be :
Ranger who patrol and defend the wall against enemies
Builders- maintain the Wall and castles, build it
Steward - help and support other players in their duties