You can add unlimited publishers either by adding them manually from the network OR allowing them to register with the customized fields.
Adding via network
STEP 1: Goto Publisher, click on Add from the publisher menu options on the left bar.
STEP 2: Fill up the information
- Password: Password should contain at least 8 characters. This password would be sent to the publisher’s email.
- Custom Fields: This section contains the extra fields for information which you want from your publisher.
- Settings: With this option, you can assign the account manager to the profile.
You can also add publishers by sending them registration forms.
You can also customize publisher forms from your admin panel.
Image: Publisher registration form
Refer this link to know how to add fields in registration forms: http://vnative.com/ad-network-customized-publishers-registration-form/