i brought the TM but how do i use it?

i think you go to the manage items option which is near your inbox/mailbox then go to toxic and do "use item"

First, you go to "Your Pokémon" in the main menu. Then, once there, you will see things like [Evolve Pokémon] [Open Box] and then [Change Moves] click on change moves. Then, make the pokemon you want toxic on be your starter, and then, if you scroll down, you will see something called "Pokémon TMs" Select Toxic, and then it'll ask what move you want to replace for toxic, then Hooray! You now have toxic on your pokemon.