how to push to a cloned repo

I had been working on Github contributions. I have cloned a repo from someone and made changes. Then I tried to push it, it shows:

$ git push -u origin
remote: Permission to PronayTheVirus/LMSLibraryManagementSystem.git denied to SanjayRam07.
fatal: unable to access 'https://github.com/PronayTheVirus/LMSLibraryManagementSystem.git/': The requested URL returned error: 403

Then I created a new branch and added all files by git add . and committed. Then, again I tried to push and it shows the same. What I need to do.

Expects:
To solve this issue and to push it.

>Solution :

If you want to contribute a merge request to another repo you’ll need to fork it first:

1. Go to the project

2. Fork the project to your own account

3. Clone your fork

4. Make changes

5. Push to your fork (make a new branch if needed)

6. Push to your fork

7. Create a pull request from your fork to the upstream repo

   (There will be a ‘Contribute’ button on your fork’ed repo page to simply this action)