When you first get your period, you may feel happy about entering womanhood, scared about how to deal with it, relieved or worried about the timing, or all of the above. This is perfectly normal.
Usually, girls start getting their period (menstruating) between ages 10 and 13, or at the same age their mom or other relatives got theirs – though it can also be younger or older than this. If you have an older sister, the age she started can give you a clue about when you'll get yours.
If you are worried about when you got your period or when you will get it, you should talk to your parent and/or your doctor.