Welcome to the Cake Decorators Q&A
Hi Michala
I haven’t seen the tutorial yet, however, royal icing can be stored in an airtight container for up to two weeks. It is best to wipe the sides of the bowl completely so no hard bits form, then press cling film onto the icing and disperse any air which might be trapped. Cover in the same way with another piece of cling film, keep in an airtight container. If you don’t get all the air out the icing will form a crust which, if beaten again will cause you problems in the nozzel while piping. I was always taught not to refrigerate RI because it will absorb moisture and spoil it’s consistency. Other members may advise differently. These days I make it up with dry egg whites or Merriwhites. Re beat the icing with a palette knife each time you use it to make it smooth.