The buffer recipe linked above will do it for you however adding Epsom salt raises your GH which does nothing to alter or buffer your PH. If all you need to do is buffer, (raise and stabilize) your PH then baking soda is all you need.
Try testing your tap water after its been sitting for 12 hours. Just to make sure there's nothing in your tank that is lowering you PH. Also you'd do well to get your own test kit, (test tube and liquid type), rather than have anyone else test it. It will be more reliable.
Once you determine that your tap water does in fact have a low ph then follow the directions in the buffer recipe for determining how much baking soda per five gallons your tank needs in order to buffer, (raise KH), your PH. Then once you know that you'll know how much baking soda to add per five gallons every time you do a water change on your tank. Keep in mind that like most salts baking soda does not evaporate out of the tank when you have normal evaporation so only count the water you remove, not any that has been lost to evaporation.
Please post back with any additional questions
What species of fish are you planning on keeping? While the baking soda route is inexpensive and relatively easy another solution to your low ph is to stock your tank with fish who prefer a low ph.