How to use SerenityStories class of net.serenitybdd.jbehave package

public Git call() throws JGitInternalException {
    try {
        URIish u = new URIish(uri);
        Repository repository = init(u);
        FetchResult result = fetch(repository, u);
        if (!noCheckout)
            checkout(repository, result);
        return new Git(repository);
    } catch (IOException ioe) {
        throw new JGitInternalException(ioe.getMessage(), ioe);
    } catch (InvalidRemoteException e) {
        throw new JGitInternalException(e.getMessage(), e);
    } catch (URISyntaxException e) {
        throw new JGitInternalException(e.getMessage(), e);
    }
}

public static bool IsValidRemoteRepository(URIish repoUri, CredentialsProvider credentialsProvider = null)
{
    var repoPath = Path.Combine(Path.GetTempPath(), Path.GetFileNameWithoutExtension(Path.GetRandomFileName()));

    Directory.CreateDirectory(repoPath);

    var git = Git.Init().SetBare(true).SetDirectory(repoPath).Call();

    var config = git.GetRepository().GetConfig();
    config.SetString("remote", "origin", "url", repoUri.ToString());
    config.Save();

    try
    {
        var cmd = git.LsRemote();

        if (credentialsProvider != null)
        {
            cmd.SetCredentialsProvider(credentialsProvider);
        }

        cmd.SetRemote("origin").Call();
    }
    catch (TransportException e)
    {
        LastException = e;
        return false;
    }

    return true;
}