Your cadet shirt is worn at all times unless in Civvies, there are two different types of shirts; Dark Blue and Light Blue. Each of these shirts should be treated in the same way:
Ironing - The shirt should be ironed at all times with no creases
Defluffing - The shirt should have no fluff on, this can be achieved by getting some cellotape and patting the shirt.
Loose Threads - The loose threads in a shirt can be got rid of by cutting them off. Do not pull any threads.
The shirt also has tabs for your brassard and jumper, see Jumper for more details