How do i tell my parents i need inpatient thearpy for my anxiety and depression ?

Schedule conference.: Your therapist, you, and your parents should schedule a meeting and discuss the entire situation. Would anticipate parental support.

Speak your truth: If you need inpatient treatment you go and get it. You're 23 years old and considered an adult. You don't legally need their permission. However, in including them you are also inviting them to be a part of your treatment. I suggest "speaking your truth respectfully"; tell them what you need, how you arrived at the decision, and what you need from them/ why you chose to talk to them about it.