You must first make sure you copied the two plugins from the .zip file downloaded from the WPILib page into the Eclipse "plugins" directory and restarted Eclipse so they are registered. Note: you must extract the plugin .jar files from the .zip file provided on the WPILib page.
To create a new project:
- Choose menu items File->New->C Project.
- In the "C Project" dialog that appears, type in your name for the project and adjust the location if necessary.
- If you have properly installed the two plugins, there should be a choice in the "Project Type" list that says "Microchip Embedded Systems".
- When you select "Microchip Embedded Systems", you will be given a choice of 7 different "Toolchains" to use on the right hand side. Just select the appropriate one for the type of project you are creating and click "Next".
- On the next dialog, take the default configuration and click "Finish", or click on the "Advanced Settings" button to see more options.
You will also have to follow the instructions on the WPILib page concerning search and include paths, as well as the linker file and library order. These can all be checked/adjusted in the Project Properties dialog. (Right-click on the project object in the left-hand "Project Explorer" pane and select "Properties").
HTH. If you have more specific questions beyond that, please post again.