This article shows you how to add a new device on your Apple Developer Portal.
Steps
Method 1 of 2: Use the iPhone Developer Program Portal

Step 1. Identify your device's 'UDID' number
It is a 40-digit number (https://www.innerfence.com/howto/find-iphone-unique-device-identifier-udid).

Step 2. Enter the iOS Dev Center and log in (https://developer.apple.com/iphone/index.action)

Step 3. Select the 'iPhone Developer Program Portal' link on the right side of the page

Step 4. Select the 'Devices' item, or the 'iOS Provisioning Portal' link

Step 5. Press the 'Add devices' button on the right side of the page (if you have selected the iOS Provisioning Portal item, the link will be on the left side of the page)

Step 6. Enter a description and the UDID of your device obtained in the first step of the guide, and add a description for the device

Step 7. When finished, hit the 'Submit' button
Method 2 of 2: Use the Developer Member Center

Step 1. Log in to the following website 'https://developer.apple.com/'

Step 2. Log in to the 'Member Center'

Step 3. Select the 'Certificates, Identifiers & Profiles' link

Step 4. Select the 'Devices' item on the left side of the page

Step 5. Press the '+' shaped button to add a device

Step 6. Enter the name and UDID of the device you want to add

Step 7. Once you are done entering, press the 'Continue' button at the bottom of the page

Step 8. To register the new device, press the 'Register' button at the bottom of the page
Repeat this procedure to register up to 100 devices for a single account.

Step 9. Connect your iPhone or iPad to your computer using a USB cable
