If it's the inertia part of the belt that you need help with the seat covers unzip and lift off out of the way. The bracket frame that the inertia part bolts onto is found in the back of the seat - at least it is on my 7 seater 2nd row middle seat. The inertia part needs to be a the correct angle before the seat belt will be allowed to reel out. Had me effing and jeffing before I realised the position needed to be correct.
Just as a head's up if applicable, the 7 seater 2nd row middle seat belt is different to the normal 5 seater 2nd row middle seat belt.