Finding previous years' papers for the Civil Engineering optional subject of a specific university, year, topic, and difficulty level can be done through the following steps:

1. Identify the University:
- Determine the specific university for which you are seeking previous year papers.

2. Visit the Official University Website:
- Go to the official website of the university.
- Look for the "Examinations" or "Academics" section on the website.

3. Search for Previous Year Papers:
- Look for a section or link that provides access to previous year papers.
- Some universities may have a dedicated section for question papers.
- If the papers are not readily available, proceed to the next steps.

4. Contact the University:
- Find the contact information, such as email or phone number, of the university's examination or academic department.
- Reach out to the department and request previous year papers for the specific subject, year, topic, and difficulty level.
- Mention your purpose and provide any necessary details to help them understand your requirements clearly.

5. Check Online Educational Platforms:
- Explore online educational platforms like EduRev, which provide a wide range of study materials, including previous year papers.
- Perform a search for the specific university, subject, year, topic, and difficulty level on EduRev or similar platforms.
- Filter the search results to find the desired papers.

6. Join University Forums or Groups:
- Look for online forums or groups related to the specific university or civil engineering studies.
- Join these forums or groups and seek assistance from fellow students or alumni.
- Inquire if anyone has access to or can provide previous year papers for the desired subject, year, topic, and difficulty level.

Remember to always respect copyright laws and use the obtained papers for personal study purposes only. Additionally, it is important to understand that the availability of previous year papers may vary depending on the university and subject.