In the spring of 1775, Paul Revere was employed as an express rider by the Massachusetts committee and the Boston committee.
Dr.Joseph.Warren told him that the British army planned to arrest Sam Adams and John Hancock. Also they will destroy military stores too.
Paul Revere instructed his friends to show lanterns in the tower of Christ Church as a signal. One lantern meant they were marching by land. Two lanterns meant they are using the sea.( Charles town river.)
His friends lighted two lanterns and Paul Revere saw that.
Paul Revere went to his house and got a coat and boots. He went to Boston's North End waterfront to meet his friend who helped Paul Revere to cross the Charles town river.