You can upgrade each instruction using instruction boosters. It improves duration or efficiency of the instruction.
You can win these instruction boosters by performing in tournaments.
If you are not winning new instruction boosters participating a tournament, you have to chose a better tournament category. Your player needs high level matches to win instruction boosters.

On the Tennis Live Arena main screen, there is a button directing towards the profile of the selected player. The profile screen comprises an instruction section which allow you to check the effect of each instruction, its current level for the player, and allow you to upgrade it.
An upgrade happens for one player only, the one whose profile you have selected. An upgrade uses a certain amount of “instruction boosters”. Those boosters are mostly won by playing matches and as rewards at the end of each season.