The SparkFun Inventor's Kit (SIK) Experiment Guide contains all of the information needed to build all five projects, encompassing 16 circuits, in the latest version of the kit, v4.0a.
The SparkFun Qwiic Speaker Amp includes the Texas Instruments TPA2016D2 stereo, filter-free class-D audio power amplifier. This tutorial will help you get started and configure the amplifer settings using an Arduino microcontroller.