How can I hook up the DF Mini and a small speaker to the arduino board? How can I connect a 3.5mm jack to the breadboard? where do I put the mp3 file in the code? I used to know this kind of stuff but its bbeen a while, thanks.
No links to the used hardware, no post of the code you refer to. Did you really read the sticky post at the top of the topic? If you expect help from us read it and follow the contained recipe of how to make a post that provides the information to enable us to help you.
suggests that the DAC_R and DAC_L outputs are at earphone level. You could connect a 3.5mm jack to these and ground and it looks like it's meant to work.
here is a library for that:
check the examples to see what it can do
the same sound chip is in the Catalex YX-5300 module, with a serial interface. I can’t tie up that many pins
The DFPlayer Mini does also have an onboard amplifier so it can drive a speaker directly rather than using the DAC_L and DAC_R outputs through an external amplifier.