I don't recommend using dried lentils in this recipe. These would need to be cooked into the sauce, which wouldn't have enough liquid. That being said, if it's all you have and you don't mind the extra work, you could cook the lentils in another pot with water, following the package's instructions, then add them to the pasta sauce. Make sure to cook the lentils until soft. And keep in mind that split red lentils don't hold their shape when cooked, unlike brown or green lentils. Use what you prefer.