If you have applicants starting mid-way through the year, for example, if you have a new cohort of Nursery students starting in January, just follow steps 1-6 shown here (where applicable): Applicants
Then in the Applicants section, select the students to enrol, then click the Bulk action button. First select which year group they will be in, then select which registration form they will be in, then click Enrol students.
The students are then enrolled in your school. You'll then need to enrol them into their actual classes, or if they are nursery students set up regular or irregular attendance patterns so they appear on the right registers.