Correct way to add external jars (lib/*.jar) to an IntelliJ IDEA project

Question

When creating a new Java project in IntelliJ IDEA, the following directories and files are created:

./projectname.iml
./projectname.ipr
./projectname.iws
./s         


        

Answer 1

Some great help found here. However, I still could not make it to work despite loading JAR properly. I found out later that I accidentally created module in the file structure instead of regular folder and this very module was pre-selected in the project setting.

Here is the footprint:

File -> Project Structure -> Modules -> (select proper module if you have more) -> Dependencies -> + -> JAR or Libraries