Go to Metform=> Settings=> Newsletter Integration=> CovertKit=> Click on the Get API to get App ID and App Secret
Create a CovertKit Account and Log In with your Email and Password
Now Go to Account Setting
Copy the API key
Paste the key Here
Now go to Landing Pages & Forms=> Create New
Make Sure while create a Form Check the Auto-confirm new subscribers Checkbox
You can see the Created Form Appeared
Form Setting=>Enable ConvertKit=> Refresh=> Created form List appeared Here
You can see new Subscriber will appeared here