This depends on your stance really but I will try to mention as many key points as possible for both stances.
If you think that people should clone people :
You could mention :
1. It could help with scientific research
1.a People can clone a group of people and keep them in a place with no other people (to prevent relationships so that no one gets emotionally hurt if the clone dies during experiments). People can test things like drugs, cosmetics or medical procedures on the clones so that if the clone dies, it doesn't really hurt anyone. Also, this could help stop animal testing which is quite a big problem nowadays.
2. It can help with people who have lost their loved ones and are suffering because of it.
2.a People can clone their loved ones when they are at known near-death illnesses for example cancer. So that when the actual person dies, the guardian doesn't suffer as much as the clone could somehow "replace" it. Some people go throw tough times when they lose a loved one, they may suffer from depression or overeating. They could lead to some health issues so if people clone their lost loved one, it would hurt less.
If you think people shouldn't clone people:
You could mention :
1. It can cause the population to rise.
1.a In the recent years, the population has gone up by quite a lot and it keeps rising. If we allow cloning, this will only increase the population. We barely have enough resources to cater for the present amount of people , but if cloning is allowed then we won't have enough resources for the future generation. Resources nowadays are already so important, if we clone people then that will threaten the Earth's environmental state.
Audience :
Mainly the younger generation. (Ages 13-25)
What I think they know :
1. The concept of cloning
2. The story of Dolly the sheep
3. Overpopulation
What I think you should cover :
1. The effects of overpopulation
2. The feeling of losing a loved one
3. Types of scientific research that could happen if we were to use cloning.
I hope this helped, feel free to ask questions if you don't understand what I meant. :)