It's very easy.
AliExpress - Buy directly from China
Get registered.
Select item.
Buy it.
I have been buying for a year now and its great.
Some tips which I follow:
1. Always survey for the best price and reliable seller.
2. Always buy items which have free shipment.
3. Always research before I buy for brand or model.
4. Most of the products are Chinese, so their is no warranty on them.
5. The items for sale are 99% copies of original products, so keep this in mind.
6. Delivery is between 15 - 40 days.