Please start with these steps specifically: iOS QuickStart
You will need to have:
- A UE4 Project
- One of each type of device you plan to publish to
- Your Apple ID (Set one up if you do not already have one)
- XCode
You can sign into the Developer part of the site with your Apple ID. You do not have to join the Apple Development Program.
If you’re following along the steps linked above and you get to a point where it appears you have to pay for something, please post a link to that step and/or a link on the Apple site where you are expected to pay.