You don’t need to wait until you have been offered a place at university to apply for your student funding. You should be able to apply for it at the beginning of the year. Check your student finance agency for the exact deadlines.
You need to reapply for student finance each year of your course.
UK students
The student finance agency you must apply through depends on where you are living when you first apply:
EU students
EU students cannot apply online and must download the application forms.