Sonia, I looked at their website and I wasn't pleased with the directions to get to their hotel. Here's how to get there.
When you arrive and clear customs at Marco Polo, just go outside and catch either the ACTV or ATVO bus. About 3Euro and you can pay onboard, Both take you to the same place - the Piazzale Roma.
When you get to the Piazzale Roma, go over to the Vaporetto ticket booth and purchase a vaporetto ticket (6.50 Euro). One hint here is to go online with www.veniceconnected.com and buy a multiple-hour pass. The 6.50E individual fare is expensive.
Once you have your vaporetto ticket, you want the No 1 or No 2 vaporetto going to Lido. The No 1 is a local and will stop at every stop. It will take you 45 minutes to get to the San Zaccaria/Pieta stop. The No 2 is more of an express in that it doesn't stop at every stop. You'll save about 10 minutes on the No. 2.
Once at the San Zaccaria/Pieta stop, you are within a short walking diatance of your hotel. Hint. You will see the San Marco stop just before you get to your San Zaccaria/Pieta stop.