there's numerous methods of opening crisps but I'll explain to you the easiest ways:
1. Take a packet of crisps and at either end pinch each side and pull you're hands apart (can be difficult if hands are greasy from crisps, best to open all your packs at the same time).
2. You can also open a packet by squeezing the packet directly in the centre with one hand (if said task is proving to be difficult use two, it should pop if enough force is used).
3. This method is to be used if all else fails just place the packet on the floor and slowly start leaning you weight on the bag (don't stamp on it or you run the risk of crushing the crisps).
Once you open the packet you can either eat out of bag with your fingers, or you can empty the bag on a plate if you're feeling fancy