Instructions
Double-click your desktop icon for "StarCraft 2," or access the program through your directory.
Create a Battle.Net online account. You will be prompted to create an account upon initial login, but you can also create an account at StarCraft2.com.
Login to "StarCraft 2" with your Battle.Net account and download all backed up patches. The patches will automatically be saved and installed as you acquire them, so don't worry about saving them. You will be prompted for the download as soon as you login.