I can't figure out how to use the tm06 on my level 10k giratina, it just keeps saying "I should teach my Pokemon this move", I'm like really confused... If someone can send me a video or something that would help a lot. Thanks

Keep the Pokemon you want to teach toxic in First slot. Then, go here: https://pokemoncreed.net/changemoves.php

Then click on [use item]

Select the move you want to replace with toxic.

That's it :)