How to open SBT Tool Window in Intellij?

In Menu: View -> Tool Windows there should be two entries:

1. SBT
2. SBT Console

The first you can use to refresh IDEA project structure from SBT and view dependencies.

The second gives you a console where you can run sbt commands.

Update:

As Justin already aded:

As of IntelliJ IDEA 2017.1 Build #IC-171.3780.52 there is a new and (imho) better way:

(If you are working with an SBT project, that is)

When you open the SBT Tool Window, you will find a new scala terminal icon:

This will open an sbt console session with your sbt project import settings.

One major benefit is that you will actually (finally) get links to your code lines for compiler warnings and errors.