It was a complicated diplomatic deal by the British government. By 1762 Britain had virtually stripped France of its American empire, having conquered New France and the sugar islands of the Antilles. The peace offered by William Pitt was severe, and included harsh trade restrictions which would have hurt Spain as well as France, so the Spanish stepped into the war in 1762 in an attempt to moderate Britain's demands.

The following year of war went badly for Spain, with the British foiling their invasion of Portugal, and then conquering both Havana and Manila. By then it was virtually all over except the crying. Everyone wanted the war to end, and Britain, now with new leadership eager to make peace, offered very generous terms.

Britain would took all of Canada and returned the sugar islands to France, but demanded in return that the Spanish give them Florida. In exchange, the French gave Spain Louisiana. The British also returned Cuba and the Philippines to the Spanish. It was a fairly happy deal for everyone involved, leaving Britain with a vast new American empire, France with its ultra wealthy Carribean colonies, and giving Spain a good chunk of the American interior. Does that answer your question?

Source - Fred Anderson, Crucible of War