You can use some third party applications available on the internet. But actually you can hide your secret files without any third party application, nor by changing the file attribute to hidden, but by disguising it into an image file. First, you need to compress the files using 7-zip or Winrar to zip or rar files and then merge the compressed file with an image file. For example I have two files, secret.rar and rose.jpg and located in C:\, to merge these two files please follow these steps:
Press Enter, it will create secret_rose.jpg file
When someone open secret_rose.jpg, it will open up rose.jpg inside secret_rose.jpg and Windows will use the default picture viewer to open the file. To open compressed file inside secret_rose.jpg simply rename it to secret_rose.rar and the extract it.