include instructions for opening an existing Swift project

Author: matthewbastien

userdocs/userdocs.docc/Articles/Topics/installation.md

@@ -7,4 +7,6 @@ The Swift extension is supported on macOS, Linux, and Windows. To set it up:
 2. Install [Visual Studio Code](https://code.visualstudio.com/Download).
 3. Install the Swift extension from the [VS Code Marketplace](https://marketplace.visualstudio.com/items?itemName=swiftlang.swift-vscode).
 
-Once your machine is ready, you can get started with the **Swift: Create New Project...** command.
+Once your machine is ready, you can start writing Swift code:
+ * Use the **`Swift: Create New Project...`** command from the command palette to initialize a new project.
+ * Navigate to **`File > Open Folder`** in the menu bar to open an existing project on your machine.