You can get your Universal Account Number from your employer which he will get issued from EPFO. After obtaining UAN from your employer you have to register it at UAN portal to avail the benefits of UAN like e-Passbook download, Check EPF balance, KYC updating and filing and watching transfer claim status.
To register for UAN enter your UAN received from your employer, your mobile number, your current PF Number and enter the words as you see in picture. Now click on GET PIN. You will receive an authorization pin on your mobile. Enter that pin in the box in lower screen. Click on I Agree and click on submit. After submitting a new screen will appear like this. Here verify your details, enter your email id and create a password with which you can log in at UAN portal. Your username is your UAN and save the password created at a safe place as it will be required every time you log in at UAN portal.
Activation UAN Based Registration