If you only have the original StarCraft installed, you will only need to download and run the [Original] patch. If you have the Brood War expansion installed, you will only need the [Brood War] patch.
Note: By installing the latest patch all previous updates will also be installed.
If you have registered the game on Battle.net, you can download the game from there. This client installer is usually updated with a current version of the game which requires minimal patching (if any) after installation.