This is a demo tutorial. While there is no step-by-step commentary available (yet), the live demo below is fully functional. Feel free to open it for full source code.
By default legend displays its markers as squares or mini versions of series. This demo shows how we can replace them with checkboxes.
See the Pen amCharts 4: Legend markers as checkboxes by amCharts team (@amcharts) on CodePen.24419