But it takes some time and if you are looking for an easy to us tool then you can use EncryptOnClick, its and one click tool which allows you to encrypt or decrypt your files or folder. UI of this tool is very simple. Once you download and install it, just launch it and you will get straight forward option, Just add your file or folder to it.
It will encrypt your file within some time, You have to repeat the same to decrypt the file, Once you decrypted file your encrypted file will go away and you have to encrypt file again. Its an nice freeware tool.