There isn't really a Boardwalk entrance to Epcot. That's the International Gateway. Where the walkway around the World Showcase has another path instead of continuing on to France from the British Isles, that's where you will find the International Gateway. From the outside of Epcot, it's very close to where you leave your boat that you might take from the Epcot resorts. But if you are staying at the BC or BCV, it's much quicker to walk than to take the boat. You have to head back towards the YC boat dock to catch the boat, then float over to the BW area, then on to Epcot.
Plus where the bridge over the waterway heads to BW, there is another pathway that goes under the bridge to IG. You don't have to hike up the hill and can stay at a more level elevation.