Although you can easily do that following the guide here: MoPub mediation guide on mediation, if I was the one here, I'd instead go with Google AdMob mediation. They support tons of ad networks, and the integration is far easier than MoPub. For AdMob, you just have to add the ad networks in the Admob console and add the SDKs for the ad networks in your app. But if you choose to go with MoPub, just follow the guide above. It is beginner friendly, and self explanatory.