From MXP, take the Malpensa Express train to the end-of-line at Milano's Cadorna station, €11 ticket, ~40-45min.

From this station you could taxi to the hotel (~€10 + supplement with baggage).

If you're more comfortable/experienced with public transport, take the #61 bus (direction Largo Brasilia), and get off at the stop on Via Washington just past the hotel. Ask the driver for Milan Marriott, and he can alert you when to get off. €1.50 for bus ticket, validate it on board.