added note and corrected prefix steps

Author: marciocloudflare

src/content/docs/magic-transit/how-to/advertise-prefixes.mdx

@@ -39,14 +39,15 @@ If you do not have an ASN or do not want to bring your ASN to Cloudflare, you ca
 Current customers who are still using Cloudflare's AS209242 can continue using this same ASN. No further change is required.
 :::
 
-## Add an IP prefix
+## Advertise your prefix
+
+You can only advertise your prefix after running pre-flight checks with Cloudflare. If your prefix status is greyed out and shows an _Withdrawn_ status, it means your prefix is locked. Contact your account team to unlock it and close the pre-flight checks phase with you.
 
 1. Log in to the [Cloudflare dashboard](https://dash.cloudflare.com/login), and select your account.
 2. Go to **Magic Transit** > **Configuration**.
-3. From the **IP Prefixes** tab, select **Create**.
-4. Fill out the information for your prefix and select **Add IP Prefix**.
-
-After you add the prefix, you can edit its status.
+3. From the **IP Prefixes** tab select your prefix > **Edit**.
+4. Under Status, select _Advertise_ to advertise your prefix.
+5. Select **Edit Prefix**.
 
 ## Edit the status of a prefix