请教申请美国公民（citizenship）问题

My family has been permanant residents in US almost 5 years.(4 yrs 10 months). We are going to apply for citizenship. We have a daughter who was born in China. She has a green card also and is 8 yrs old now.

Since all applicants should be at least older than 18 yrs, how can I apply for my daughter's citizenship? Shall we file her application together with ours or seperately? Which form shall we use?

Thanks in advance.