That depends on the age of your child. As your child gets older, they should be able to equip their gear and perform safety checks. You should always double-check to ensure that they are doing it correctly, but an older child should have the confidence to wear the gear and use it as it should be used.
Even the youngest child should be able to do something when it comes to putting on the gear. You should always be there to help, and some children will need more help than others, but you should not be expected to do everything for them.