The flat is 15 minutes from Venise city center by bus (4L). There are 2 groceries stores nearby which is very practical. You should get your stuff there before going to Venise city center.
If you are staying in Venise for a couple of days, I suggest you to take a day ticket so you can take the city bus but also the vaporetto (boat bus) in Venise. You can get the ticket at the tabacchi or at the train station. By the way the also sell 2 and 3 days ticket.
This flat is a good for the price and Leonarda answered my messages quickly.