Hey, no worries. Sorry this is late, I haven't been on.
So, okay, you see that picture of Starmie you posted? You see that part of her star that points directly at Misty? Now, you see the two stars on either side of it (one below it, one above it), that's the "Second star" it's referring to. Imagine taking two starfish and stacking them together, but turning one of them so that it appears like there's a "pointer" from every angle. That's essentially how Starmie is.
So, okay, you see that picture of Starmie you posted? You see that part of her star that points directly at Misty? Now, you see the two stars on either side of it (one below it, one above it), that's the "Second star" it's referring to. Imagine taking two starfish and stacking them together, but turning one of them so that it appears like there's a "pointer" from every angle. That's essentially how Starmie is.