əˈpriːʃə.tɪv
Here's a breakdown:
* ə as in "about"
* priː as in "tree"
* ʃə as in "ship"
* tɪv as in "give"
You can also hear the pronunciation by searching for "appreciative" on a dictionary website like Merriam-Webster or Oxford Dictionaries. They often have audio pronunciations available.