Once your child turns 2, they can apply for preschool.
Your child can apply for preschool once he/she turns 2.
Once a child turns 2, he/she is eligible to apply for preschool.
「プリスクールは子供が2歳になった時点で随時応募できる」。
❶Once your child turns 2, they can apply for preschool.
❷Your child can apply for preschool once he/she turns 2.
❸Once a child turns 2, he/she is eligible to apply for preschool.
apply ー応募
He/ she のところは “He or She” と読みます。
…but only if there’s an opening. ただし空きがあれば。
例えば:
Once your child turns 2, they can apply for preschool but only if there’s an opening.
(プリスクールは子供が2歳になった時点で随時応募できますが、空きがあればですが)。
アメリカ合衆国 
