To book a ticket under ladies quota, you will have to select "Ladies" from under the Quota option on IRCTC (option available under thr same dropdown as General, Tatkal). If booking at a PRS counter, you will have to mention the same on the booking form. This quota does not have RAC/WL, so once the six seats are sold out, the status will show "Not Available". Goes without mentioning that only ladies can be booked under this.
Contrary to popular belief, this quota is very popular and mostly will get sold off early