Adding image resources to your C# application is close to trivial. One method is to open your Resources.resx file and simply add bitmaps you wish to use. However, this leaves your with all images in Resources folder. Some people like it that way but I prefer to avoid it - I prefer the old-style system of keeping it all in your resource file.
To have all images included in resource instead being in a separate folder, just select offending resources and press F4 to bring Properties window. Under Persistence simply select Embedded in .resx and your resources are magically (no real magic involved) embedded into resx file as Base-64 encoded string. Only thing remaining is to delete leftover folder.
You use resources from application same as you normally would.