I have an expiremental pet that i want to turn into a dark matter tigrean and also bought the dark matter potion but don't know what i need to do to change her into a tigrean first,please tell me what i need to do or buy.

any tigrean elixir! just search "tigrean elixir" and any of the options will change your pet, then you can use the potion. this is true for any pet you'd like to change the species for. elixirs change species, and potions are for colors.

any of the tigrean elixirs will do. they're all currently in user shops for around 70k, but there is one twilight tigrean elixir for 65k which is the cheapest of the lot.