How did washington gain control over boston

In June 1775, George Washington found his thoughts turning to Mount Vernon. 
Washington was charged with forming these companies into an army and directing the siege of Boston. Washington worried that Virginia's Governor Lord Dunmore would attack his plantation and even imprison his wife. But still he had no choice but to obey the "kind of destiny" that had given him this command and head for Boston.1 Upon arriving in Cambridge in early July, Washington proposed an attack on Boston. 
In early September, Washington began drawing up plans for two moves: first, to dispatch 1,000 men from Boston and invade Quebec, and second, to launch an attack on Boston.[38] Washington felt that he could afford to send some troops to Quebec, as he had received intelligence from British deserters and American spies that the British had no intention of launching an attack from Boston until they were reinforced. On September 11, about 1,100 troops under the command of Benedict Arnold left for Quebec. Washington summoned a council of war, and made a case for an all out amphibious assault on Boston, by sending troops across Back Bay in flat-bottomed boats which could hold 50 men each.Washington believed it would be extremely difficult to keep the men together when winter came.