Sharing... Do you really expect a toddler to share?
It's an abstract concept that, if pushed on a child, can often cause resentment and 😡anger outbursts. I believe that if a child has a toy in their possession, that they can play with it until they're done. If a sibling or friend wants to play with that toy, you as the parent, can intervene and say, "[Child's name] is playing with that toy; you may go play with the toys over there." Then you may facilitate the concept of sharing by intervening and saying to the child with the toy, "[Child #2's name] wants to play with that toy. When you are done, may she have a turn?"
To help promote abstract concepts, I always like to use books. My favorite sharing books are:
1) Too Many Mangos: A Book About Sharing by Tammy Paikai
2) Those Shoes by Maribeth Boelts
3) Too Many Carrots by @katy_hudson_illustration