Practise placing coordinates in the coordinate system.
Press the cursor button in the toolbar to control the tool. Select a point in the coordinate system and the coordinates appear. Click on the point again to hide the coordinates. You can show or hide the coordinates with the eye icon.
Change the colour of the points in the coordinate system in the settings menu. With the 'manual' option you can select the colours that you want to have available in the toolbar. The active colour is used when selecting points in the coordinate system.
Click on the 'Clear' button in the toolbar to clear the coordinate system