I would like to make a private folder.
so how can I password protected folder without any additional software?
If by "no additional software" you mean using the filesystem tools alone, then the answer is: you can't.
However, you can easily create a private directory accessible to your non-privileged user only. All you need for this is restrict access for all other users. You can use the means of your graphical file manager, or you can do it from the command line:
After this, the content of your directory will be visible only to your non-privileged user (and root, of course).
Hope this helps