安装好了worldpress博客，后台插件和主题出现问题

安装好了worldpress博客系统后，访问 www.hilear.com/blog 正常， 但是在后台管理中，修改 "theme"主题和添加wp插件的时候，报错。报错如下：

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, webmaster@qxu2309310199.my3w.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.

百度查询后得知是 .htaccess 需要进行修改

我应该如何修改这个文件，盼尽快回复我，以便博客系统能顺利工作，感谢！