You can reset skill points in the area “Cathedral of the Deep”. That’s the area where you fight the Deacons of the Deep boss. The nearest bonfire is called “Cleansing Chapel”. Take the elevator up to the Cathedral’s rooftop. From here you need to drop down to a small balcony in the Cathedral’s main hall and again from the balcony to an area below. The path leads to a room with a hidden bonfire and a worm-like being named Rosaria. Talk to Rosaria – she will let you join her covenant (Rosaria’s Fingers) and then you can talk to her to respec skill points and change your character’s appearance.
Each reset requires a pale tongue item. You get pale tongues by invading other players while being part of Rosaria’s covenant (PvP). A few of them can also be found as loot. For example, there’s one downstairs in the cathedral near one of the giants. Another one can be found in the Undead Settlement near the fire demon you fight with Siegward.
You only have five resets so use them wisely!