Grammar fix
book in
arrange an appointment
To arrange or register an appointment slot, e.g. with a doctor, dentist or clinic.
phrasal verbB1common
Hear it in context
Notice where the phrase sounds natural.
I'd like to book in for an appointment with the doctor, please.
A: Can I book in for a check-up next week?
B: Of course — I'll book you in for Tuesday.
Fix the pattern
One small grammar move makes it sound right.
Not: I want to book in a appointment.
Say: I'd like to book in for an appointment.
Say 'book in for [something]'; don't put the appointment straight after 'book in'.