string file = @"Path Of the file";
System.IO.FileStream fs = new System.IO.FileStream(file, System.IO.FileMode.Open, System.IO.FileAccess.Read);
using (var ctx = new AuthenticationManager().GetAppOnlyAuthenticatedContext(siteUrl, "CLIENTID","CLIENTSECRET"))
{
    try
    {
        ctx.Load(ctx.Web, p => p.Title);
                     ctx.ExecuteQuery();
                        Console.WriteLine(ctx.Web.Title);
                     Microsoft.SharePoint.Client.File.SaveBinaryDirect(ctx, "RelativePathToDocumentLibrary" + "/test.docx", fs, false);
                }
                catch (Exception ex)
                {
                }
}