The steps to fill in the online application for a legal professional qualification certificate are as follows:

1. Log in to the legal professional qualification management system through the Ministry of Justice website. Enter your ID number and password on the login page.

2. Check the basic information and fill in the relevant information. After successfully logging in, find the "Qualification Application" option on the homepage and enter this page. Check whether the basic personal information is correct on this page and complete other necessary information according to the prompts.

3. Upload materials After completing the above steps, upload relevant files one by one according to the list of required materials.

4. After confirming that the submission is correct, please carefully read and agree to the "Electronic Signature Statement" and "Privacy Protection Statement", and click "Confirm Submission" to complete the online application process.