You have several options for finishing your ceramic pieces.
For figurines or other pieces that will not be used for food, or washed, or exposed to weather, you can paint them with acrylic paint. You do this AFTER they are low-fired:
For pieces where you want solid, defined colours, you can use underglaze (with the option to finish it with a clear high fire glaze to make it shiny). You do this BEFORE they are low-fired:
For pieces that will be used for eating (food safe), and when you want an interesting blend of colours, try high fire glaze. The results are sometimes unpredictable but often stunning! You do this AFTER they are low-fired: