People are the product of their environment. Children can easily become more organized and grow into organized adults when you start working with them when they are young.
Changing their mindset at a young age can turn them into organization pros.
Start with toy storage bins. Introducing storage bins for them to store their toys and small items is the first step. Using colourful labels that match the items that they are putting away makes it easy for them to put their toys in the correct bins. You can also use open storage that allow them to easily see inside.
Turn "Clean Up Time" into a game and make it fun. They will quickly pick up their toys and put them away.
Once they have an organizational mindset, they will continue to put their toys away without any motivation.