You'll receive a mail notifying you about the incoming App transfer.
Either click the link in the mail or directly log in to https://appstoreconnect.apple.com with your Apple ID and find the yellow box - click the link "Agreements, Tax, and Banking"
Now find your App in the bottom list and click the right most button:
On the following page, you'll need to add the following information:
App Review Contact:
First and Last name: Your first and last name
Phone: Your phone number
E-Mail: Your E-Mail address
App Store Contact:
Like above, fill in all needed information for your company contact
After having filled out all fields, please scroll down completely and click the "Accept Terms and conditions" checkbox, then click the blue "Accept" button on the upper right.