Choose and visit a website that offers streaming online videos of movies. Examples include the iTunes store, Netflix, Blockbuster Online and Amazon. (See Resources.)
Download the required software as prompted by the online video website you choose. For example, iTunes will require you to download the iTunes software program. The other video sites may require you to download and install plugins such as Flash or DivX.
Create an account with the service, or log in to an existing account. Some services, such as Netflix, charge a monthly fee for access. You can buy or rent movies like "Twilight" from other services, such as Amazon.com.
Locate the "Search" box once logged in, type in "Twilight" and press "Enter." Click the "Rent" or "Buy" button next to the listing for "Twilight." If prompted, click "Confirm" or "Rent" again to confirm your transaction.