The first recorded appearance of the plague in Europe was at Messina, Sicily in October of 1347. It arrived on trading ships that very likely came from the Black Sea, past Constantinople and through the Mediterranean. This was a fairly standard trade route that brought to European customers such items as silks and porcelain, which were carried overland to the Black Sea from as far away as China.
As soon as the citizens of Messina realized what horrible sickness had come aboard these ships, they expelled them from the port -- but it was too late. Plague quickly raged through the city, and panicking victims fled, thus spreading it to the surrounding countryside.