How to mix one higher volume and one less volume mp3 files to gether

Hello, I have two mp3 files which i recorded with an H4 Zoom recorder.

One is me talking
and the other some music i played

I want to mix both together…both starting at the same time.

My voice louder and the music not so loud in the background.

I cant figure out how to do so,

Can you help me with this please?

Thank you

This article in the manual will probably be helpful: