Open the Shapes panel in the Sketch editor theme
Click on the Shape tool in the toolbar on the left to see the Shapes panel.
Drag the floating panel around the drawing canvas. Click on the arrow in the top right to minimise/maximise the panel.
Click on More Shapes to show or hide specific shape libraries.
From here you can also enable or disable the search feature and the scratchpad.
See how to use a custom shape library in the Sketch editor theme.