The East India Company was founded in England in 1599 and soon began to build trading warehouses in India.
At this time India was not a united country. There were small states, each with its own ruler. The East India Company sometimes asked for permission to trade in Indian states but sometimes it did not.
At the same time, the French had their own East India Company. Competition between the British and the French was fierce. In 1700 it escalated into a full scale war and the armies were dragged into the conflict.
The British agreed that they would help any Indian ruler who would help them trade and they would defeat any ruler who blocked their trade.
In 1757 Robert Clive persuaded an Indian General to fight with him and overthrow Siraj-ud-Daula, the ruler of Bengal. The battle was won and Siraj-ud-Daula was captured and killed. This gave the British control of Bengal.
Robert Clive was treated as a hero in England. In 1765 he was ent back to India to rule over Bengal. From then on he took more and more Indian states under British control. The French were soon defeated and pushed out of India.