The specific steps of importing source code into walnut programming software are: 1. Open the walnut programming software and create a new project. 2. In the Explorer on the left side of the software, select the "Code" tab; 3. In the Code tab, click the Import button; 4. In the pop-up window, select the source code file to be imported and click the "Open" button; 5. After importing, you can see the imported source code in the code tab; 6. To run the imported source code in the project, you can create a scene in the Scene tab, add related roles, backgrounds and sounds to the scene, and then call them in the code.

Note that when importing the source code, make sure that there is no language or grammar in the source code that is not supported by the walnut programming software, or you may make mistakes.