There are several online platforms where you can access study materials and previous years' papers for the Civil Engineering optional subject. One such platform is EduRev.

EduRev is a comprehensive online learning platform that offers a wide range of study materials and resources for various competitive exams, including the Civil Engineering optional subject for the UPSC exam. Here's how you can access study materials and previous years' papers on EduRev:

1. Visit the EduRev website
First, you need to visit the EduRev website by typing "EduRev" in your search engine or directly entering the URL.

2. Sign up or log in
If you are a new user, you will need to sign up for an account on EduRev. The sign-up process is simple and requires basic information like your name, email address, and password. If you already have an account, you can log in using your credentials.

3. Navigate to the Civil Engineering section
Once you are logged in, you can navigate to the Civil Engineering section. You can do this by either searching for "Civil Engineering" in the search bar or by selecting the appropriate category from the list of available subjects.

4. Access study materials
In the Civil Engineering section, you will find a wide range of study materials, including notes, textbooks, video lectures, and practice questions. You can browse through the available resources and select the ones that are relevant to your needs.

5. Download previous years' papers
To access previous years' papers, you can look for the "Previous Years' Papers" section within the Civil Engineering category. Here, you will find a collection of question papers from previous years' UPSC exams. You can download these papers in PDF format and use them for practice and revision.

6. Engage in discussions
EduRev also provides a platform for students to engage in discussions and clarify their doubts. You can participate in the community forums, ask questions, and seek guidance from experts and fellow aspirants.

In conclusion, EduRev is an online platform where you can access study materials and previous years' papers for the Civil Engineering optional subject. It provides a user-friendly interface, a vast collection of resources, and an active community for discussions and interactions.