There is a program in the repository called "zuluCrypt",install it and then look for it in the menu.
start it up,go to "menu->zc->encrypt a file" and it will give you an option to encrypt a file,the option to decrypt it is there too.
using the tool,you can also create an encrypted container that will allow you to "store" multiple files encrypted.
Creating an encrypted container and then store your files in it is better in my option because you store the files encrypted and you can also edit them "in place".With encrypting individual files,you have to decrypt them when you want to access them and when you edit them,you have to re-encrypt them and then deleting the original encrypted file,its a bit too cumbersome.
The program will also allow you to create encrypted containers if you decide to go that route.