Answer:
Britain took over the government of the area that is now India and Pakistan by force. That is, by military conquest.
It then completely controlled all the traditional kings in the sub-continent, and it used India as a source of cheap labour to manufacture raw materials for its industries in Britain. As far as it could, it took the wealth of the Indian people and shipped everything to Britain.
The Indian people eventually forced the British out, through a revolution, led mainly by M.K. Ghandi.