You need to contact the state CNA registry. You can also wait to receive an application by mail which the state will send you 2-3 months prior to license expiration.
Your license is valid for 24 months as prescribed by state law.
There is no cost to renewing your CNA license. If you have become inactive (no employment as a CNA for over 24 months), you will need to pay a $40 reactivation fee. The state recommends you try to have your employer reimburse you for any fees associated wuth renewing your license.