Attend church regularity. Your priest will be less likely to help your child through the process if you're not an active member of your church.
Speak to your priest first. Your child will need to have reached the "Age of Reason" or around 7 years old, though it depends on your church and your priest. Once a child has passed the "Age of Reason," they can be morally responsible for their actions; they should understand and be able to obey the 10 Commandments. If your child is over 7, they can still be confirmed, and some priests recommend waiting a few years.
Talk to your child's teacher if your child attends a catholic school. Most catholic schools confirm their students at certain grade levels. Your child will receive all the information they need to be confirmed during their school hours and will be confirmed with all of their classmates.
Find a sponsor/godparent. Your child will need someone to stand up with them during the ceremony, different from their godparent during baptism. The sponsor should be of the same sex as the child, at least 14 years old, and have received Confirmation already. The sponsor cannot be parents or a member of a religious order.
Plan on your child going through sacramental preparation classes, similar to what they went through when they received the sacraments of the Eucharist and Reconciliation (Confession), unless your priest recommends waives this. If your child doesn't attend a Catholic school, they will likely have to go through some preparation classes before they can be confirmed.