OP are you still there? Fold the weft length-wise so that it lines up with the clip. Sew the wefts in order to secure the folds you just made. Tighten the knots so that you will never again have to repeat the previous step. Finally insert the weft into the clip and lock it in using the middle latch.
Wash the hair once a week to keep it clean. That's about all you have to do. Good luck