Why was is necessary for the confederacy to seek the support of Great Britain and France?

AnswerThe south thought Britain would help because the south was selling their cotton to them but Britain refused because they could get it from somewhere else(Egypt)

We did get some from Egypt, but mostly from India. This meant that despite the Union blockade, the supply of cottton to the Northern industrial towns such as Manchester and Birmingham actually increased. After this, there could be no gain for the British in supporting the Confederacy, and because of poor harvests in England during the American Civil War, the British needed Northern corn to feed the people, and so they simply let the war take its course.

I don't know why the South tried to receive help from France, they had no stake in it what so ever

(New contributor...) The French wanted influence in Mexico, and it would have suited them if there were a new nation, pro-French, in-between Mexico and the USA.