dma,
If you're using EasyJet, you will be departing from Terminal 2. In that case, the easiest transport will be to take the train from Monterosso to Milano Centrale, and then the Malpensa Shuttle (bus) to MXP. With your back to the tracks, go left and down two flights of stairs to reach Piazza Luigi di Savoia, which is where you'll find the Buses (if you pass a McDonalds, you're going in the right direction). I believe there are two firms offering shuttle bus service to MXP. You can buy tickets from small booths right there or (I believe) from the driver. Larger luggage items will go in the hold under the Bus and smaller "carry-on" type items go with passengers. The trip is about 50 minutes (subject to traffic of course), but I've made that trip many times and there never seems to be any serious delays.
If you buy a ticket from the Malpensa Shuttle website, don't forget to validate it prior to boarding the bus (the driver may do that for you).
EasyJet appears to have two flights on 10 July, one departing at 12:00 (EZY2603) and one departing at 18:10 (EZY2605). I'd recommend getting tickets booked SOON, as the prices will increase as the flight fills further (fares are currently shown at €96.49 PP). As with many budget flights, you'll pay extra for every coffee or sandwich. Pay special attention to the "Terms & Conditions", especially related to luggage weights. If you think your checked luggage will be over their allowable limit, it's cheaper to pay for the next weight tier at the time of booking, rather than at the gate.
Also, note that EasyJet only allows ONE carry-on item per passenger. This doesn't mean "one plus a personal item such as a Purse or Laptop case" it means ONE ONLY of the approved size (and they will check). Weight of carry-on items is not a factor, but the passenger must be able to lift items into the overhead bin without help. You might consider paying a bit extra for "speedy boarding" as it makes for a more pleasant flight experience, and also expedites the baggage drop. EasyJet no longer has check-in at airports. You'll check-in and print your boarding pass up to a month prior to the flight as I recall. You will have to deal with the baggage drop though.
Buon Viaggio!