From Boston:

Route 24 South to Fall River, a very short distance on 195 West till you exit onto 24 South again. Go through Tiverton, over the Sakonnet River Bridge into Portsmouth. Exit right, just past the Bay Pointe Inn. At the bottom of the exit go right and straight up the hill to the Mount Hope Bridge. Once over the bridge you will go a short distance and see that the road forks, you will want to go off to the left into Bristol. After about 3/4 mile going straight the road bears off to the left, follow it around, will take you past the Lobster Pot Restaurant. Continue straight about 1/2 mile and watch for the signs for Church Street, turn left on Church and it will bring you right down to the ferry landing.

From Providence:

Take Route 195 East to Exit 7 (Barrington/Rte 114 South) Travel essentially straight through Barrington, to Warren, to Bristol. Route 114 that you are on will become Hope Street, watch for Church Street, you'll turn right on it and it will bring you right to the ferry landing.

If you want a more flexible schedule than that of the ferry, or just wind up "missing the boat", you have another option. Capt. Bruce Shaw, on Prudence, operates a licensed water taxi service where "your schedule is his schedule". You can arrange to be picked up or delivered almost anywhere in Narragansett Bay. This could include Newport for an evening on the town, dinner in Bristol, a shopping trip to scenic Wickford, a leisurely trip around the bay, or a charter tailored to your needs. Call Bruce at (401) 683-2021 for more details.