how to restore wordpress backup(.rar) manually?

As MikeNGarrett said, you need to look inside your rar file to see what’s inside.

This is basic procedure. Go to your public folder (htdocs for xampp), and create a directory(yourprojectfolder). Extract your rar file inside it. if you can see folders like wp-content, wp-includes and files like wp.config.php etc.. then you’ve done first part.

Then access your local phpmyadmin (usually http://localhost/phpmyadmin/ ). create a new database, then import from your backup (either .sqlfile or .zipfile which has sql file inside).

After import finishes, open table wp-options(note: the wp part could be different). then change siteurl and homepage url to http://localhost/yourprojectfolder.

Then open wp-config.php and give proper credentials on database details. you’re done. now you can access your wp site by http://localhost/yourprojectfolder/