I’m a layman, so take my suggestion cum grano salis: it looks like you’ re trying to RUN, on IntelliJ, a mere Object Circle, and not an Object extending Scala Application; you should open a Scala Console in sbt, and instantiate the Object.
If you go to the Scala Website, under the Documentation section, you’ll find a lot of Tutorials and Guides.
Greetings! I think the issue might be the way the project is organized: SBT requires the folder structure should be src/main/scala but you seem to have src/scala.