The steps for this situation are as follows:

Tools: mobile phone, China Construction Bank app.

1. Log in to the "China Construction Bank" app.

2. Click on the "Account" page.

3. Find and click the "Security Information" option on this page.

4. You should be able to find the credit card security code on the "Security Information" page.

Please note that you have logged in to your account correctly, and in order to protect the security of your account, all inquiries should be conducted in a secure network environment.