Simply learn yourself.
For apple ID

How to Find Your Apple ID

Find Your Apple Id

An Apple ID is a username that helps user to access iTunes Store, enable iCloud on all your iOS devices, sync data and content with multiple device, etc. Every apple ID is unique and assist user to enjoy apple services. Loosing apple ID can be really frustrating and in case you've lost or can't remember your Apple ID, here are few steps that will help you to retrieve it.

Step1: Open browner in your computer and enter https://appleid.apple.com/ into your browser's address bar. It will take you to My Apple ID website.

Step 2: You will find an option "Find your Apple ID"on the right side of the page.Click on the link it will take you to the new page. Enter the information asked and click on the ‘next’.

Step 3: In order to proceed further, you need to verify your birthday. Now, select how you want to retrieve Apple ID. There will be two options to retrieve:

Firstly, you can receive your login credentials through email
Secondly, you can answer some security questions and retrieve your Apple ID.

Step 4: Lastly, after getting your Apple ID you will have to reset the password for using it.