Open more than one code (file) at the same time.

Good morning, everyone. I hope everyone is well.

Sorry for the fundamental question; however, how can I open more than one repository file simultaneously, please?

I mean, in the past, with others IDEs, I was used to opening any file from any repository and new files from another repository in the same window. It helps in debugging and/or comparing the code. Unfortunately, I am unable or don't know how to proceed by IntelliJ.

Thank you very much.