So you've got a Kindle, you want to download some books to your Kindle device for reading and learning. Then you can transfer your books to Kindle device via USB or Kindle personal documents service. Not only books, magazines, but also music and movies, you can transfer and enjoy these entertainment on your Kindle freely and anywhere. How ever, for a new user, not every one of them knows clearly how to transfer ebooks to Kindle. Therefore, today, I will show you two methods of transferring the digital content to your Kindle.
Method 1. Using USB.
Both Mac and Windows users can download and transfer Kindle content from computer to Kindle via USB. If you have some downloaded some ePub files, you can convert ePub to Kindle to read for Kindle. Go to Manage Your Kindle, Click on the "Actions" dropdown beside the title and choose "Download & transfer via USB".

Then select the device you want to transfer to and click "Download" button.

That's all.
Method 2. Kindle Personal Documents Service
With the Kindle Personal Documents Service, you can transfer your ebooks to your email, when you connect Wi-Fi or 3G network, the ebooks will automatically be sent to your email. So you can read the books on Kindle without the need of USB.
Generally speaking, there are two steps to transfer content to your Kindle.
Step one. Get your Kindle email address.
You should visit the Manage Your Kindle page on Amazon.com, when you login your account, check out your Kindle email. On the top-right you can see your email. There are two emails you can use: one is username@free.kindle.com, which face to Wi-Fi users and it is free, another is username@kindle.com, it is for 3G users and you should pay the fee depending on flow you are using.

Step 2. Approved Personal Documents E-mail List
For preventing others freely send your unwanted magazines or ebooks to you, Amazon provides Approved Personal Documents E-mail List, which mean that only the email existing in the list, the files can be send to your Kindle.
Click "Personal Document Settings", and you can see the interface. Click "Add a new approved e-mail address", fill in the email you want then you can receive all the files from the email.
So, download anything you like and transfer these contents to your Kindle as fast as possible. By the way, if the book you downloaded is under DRM protection, you can use the free DRM Removal to remove the DRM distraction.