Before children can learn to skip with a rope they need to develop their gross motor skills in the correct order. Try:
Jumping with two feet together, then
jumping over a line on the floor, then
jumping over a rope lying on the floor, then
jumping over a rope on the floor while someone wiggles it like a snake, then
jumping over a rope while someone swings it to and fro, then
jumping over a rope when someone else is turning it, then
jumping over a rope while you turn it yourself.
Look online to find some videos, but the best way to learn is to keep practising!