To assemble it, you must glue the 4 round pieces to the four corners of the bottom of the sundial.
Then, you must position the gnomon (the large rod) pointing north and tilt it at an angle equal to the latitude of the place where you are.
Block the gnomon with the two pieces as in the photos: choose your favorite for the top and put the other on the bottom. Force a little to fix well. You can glue with wood glue and adjust the setting.
To use it, you must orient the sundial according to the N/S/E/W reference indicated on it. The sundial must be horizontal.
The time indicated is the approximate solar time. It is not a precise sundial but it is sufficient to decorate or show the principle to children for example.