There are no buses from Epcot or the Disney Studios to any of the Epcot resorts (Beach Club, Yacht Club, Boardwalk, Swan, Dolphin).
If you go to Epcot you will need a park admission and take the very long walk through Future World and then World Showcase to exit at the International Gateway. This Epcot entrance/exit is only about a five minute walk to the Beach Club, but it is a really long walk to get there from the main entrance.
I suggest you take a bus to the Studios. From there you can either take a 15-20 minute walk to the Beach Club or take the Friendship boat. The boats run continuous service from the Studios to the Epcot IG. They stop along the route at Swan/Dolphin, Boardwalk, and Yacht/Beach clubs.
After exiting the boat at the Yacht/Beach club stop turn right as you face the Yacht Club. The Beach Club is right next door.