Implement a simple WhatsApp sticker app with adMob

I have created a simple Android Whatsapp sticker app with Android Studio, following a Youtube tutorial and I would like to implement it with AdMob advertising. I don't know nothing about Java and Android Studio, so I don't know how to do it, even if I think it could be a simple work for expert developers. When the user open my app, there is a button called "add to Whatsapp" and I would like to show a video ad when it is pressed and then add the sticker pack to Whatsapp (if the user close the ad I would like a simple pop-up alert message to be shown and the sticker pack mustn't be added). I have already created the app on AdMob, so I have the app ID. I appreciate if someone would like to help me, thanks :)