How can I fix my Lena hair straightener?

So I just bought a brand new hair straightener almost a month ago. Its a Lena. I usually set it on the bathroom sink to heat up. But today my cat decided it wanted to sit up there so it knocked it down (wasn't so happy with him after he did this) The straightener came apart in to two. I have all the parts but I can't figure out how to put the spring into the straightener. So my question is if anyone knows how to put it back together?

Model:LE418

Thank you.