We know securing a child can present real problems in a medium-duty vehicle like yours. The only place where you can properly secure a child restraint is the center seating position, the place that has the lap belt only. But your vehicle may not have a center seating position. Or, even if you have one, you may find that the child restraint keeps you from operating the shift lever or other controls. The only answer may be to have the smaller children make the trip in another vehicle, where they can get to protection they need.
If your vehicle has a center seat, you can secure a child restraint here.
You will be using the lap belt. Be sure to follow the instructions that came with the child restraint. Secure the child in the child restraint when and as the instructions say. But do not use this position if the child restraint interferes with shifting gears.
There are no top strap anchors in this vehicle. Do not secure a child seat in this vehicle if a national or local law requires that the top strap be anchored, or if the instructions that come with the restraint say that the top strap must be anchored. See Top Strap if the child restraint has one.
To remove the child restraint, just unbuckle the vehicle's safety belt. It will be ready to work for an adult or larger child passenger.