would you like to encrypt your files or set a password for some files and the other files could be accessible as usual?
If you want encryption - here is how to do it.
You can't put a password on some folders in owncloud.
What you could do - and this is a workaround - is put the folder you want to protect with the password on an external storage, connect to that storage in owncloud, and save the credentials in session. So you will see the folder in your files, but if you want to open that folder, you will be asked to enter the credentials. If only you know the credentials - only you will be able to see the content of that folder.