It looks from your examples that you are not doing too badly. Welcome to the Forum! There was a portrait lighting tutorial in the resource area a while back (think it is still there...). Folks here have different styles, so I'm sure you'll get different answers. Using flash on the camera (in line with the lens) is usually fairly harsh, and does not do well in modeling shapes. With a built-in flash, I would try to use natural light as the main (brightest) light, and the flash as a "fill." Perhaps position the model with a window to the side. [The Canon manuals are usually pretty good at describing how to set up the flash as a fill light.] I like, BTW, your out of focus candles? in the third shot.