By a water taxi or a waterbus (vaporetto).
The vaporetto departs from Fondamente Nuove. From Ferrovia (Santa Lucia train station) you take the 52 line, the shorter route or take a 41 or 42 for the more scenic version along the Grand Canal.
Line 42 goes across to Murano which takes about twenty minutes. More detailed info at https://www.actv.it
You can also take the DM (Direct Murano) from the train station stop (Ferrovia) or from the Piazza Roma, but please check the vaporetto routes in the website i posted in my previous reply so you don’t make any mistakes.