Hi there!
There is actually a blue corner at the end of every clip that you insert on your video. You can click that and drag it towards the middle of your clip. There will be a bow in your video clip. You do the same with the other (depents where you want it, on the beginning of the clip or the end). When you slide them over eachother your clips will fade into another ;).

Quick tip, you can easly slowmotion a clip by holding down your ctrl key and drag your clip 🙂
-RvdW