Using GIT, I checked out a branch from the remote repository, which another person had worked on. One of the files has conflicts, which are already committed, so the file contains marks like <<<<<<< HEAD etc.
Now, is there any way to run IntelliJ conflicts resolving tool, to resolve these conflicts? Or do I need to resolve them by hand?

When git merge has conflicts, the files that are in a conflicting state contain markers showing the differences.