You'll hardly have to do this, but a strip wash basically means a wash that it is longer and the aim is to rid your nappies of any build up of things like barrier cream you might use with them. The reason it is done mostly I find is when people are passing on their nappies for someone else to use.
If your nappies have a smell when wet, then you would strip wash them but really, if you wash them as you should in warm water with a pre-rinse you should not have this problem.
First of all, rinse the nappies with your washing machine rinse cycle. Then, with full soap-based washing powder and full level water put your nappies on a long and warm (40 degrees) wash cycle. Once that cycle is complete have them go through another cycle without any washing powder. Then hang to dry.