How to progress from an Apple rejection depends entirely on what kind of rejection it is. Most common is pending agreements, this means you have to log into your iTunes Connect account and update your agreements.
There can also be rejections that requires you to provide ownership proof of the content (Impersonation rejection), this is something that Apple are very strikt against and you need to be very thural.
Here you have some common rejection from Apples website and how to solve the issues.
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