Using IntelliJ, how to add dependency in an sbt project

Question

I'm new to sbt and I wanted to learn it with a small Scala project in IntelliJ.

I started with the official sbt Getting Started guide, to learn the sbt basics on the console ( https://www.scala-sbt.org/1.x/docs/sbt-by-example.html ). Following the guide, everything compiles fine.

Then I created an sbt project in IntelliJ, trying to do the same thing there. When I add the org.scalatest depenpency to the build.sbt file the project can no longer compile. The error message is:

module not found: org.scalatest#scalatest_2.13;3.0.5

When I created the fresh sbt project in IntelliJ, first the build.sbt looked something like this:

name := "sbtTest"
version := "1.0"
scalaVersion := "2.13.0"

Then I added the dependency:

name := "sbtTest"
version := "1.0"
scalaVersion := "2.13.0"
libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.5" % Test

After reloading the build file and getting the error when compiling, I tried to change the biuld.sbt according to the code which already worked in the sbt Getting Started guide:

ThisBuild / scalaVersion := "2.13.0"
ThisBuild / organization := "me"
ThisBuild / version := "1.0"

lazy val sbtTest = (project in file("."))
  .settings(
    name := "sbtTest",
    libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.5" % Test
  )

This has again the same error after reloading and compiling.

My sbt version is 1.2.8.

Is something wrong with my build.sbt ? Or is the sbt version too new for IntelliJ? Is IntelliJ probably not the recommended IDE to create Sala sbt projects?