Hi Vicky,
If you're writing your journal on devArt, there should be an "Options" tab on the top - and there you paste the code it gives you into the "Skin CSS" field. ^^
(This site here *points* doesn't save the journal skins yet. I might add it if there's like a huuuge demand for that, but in the meantime, you can just use the code as a template to get started - if you ever want to change the images, just replace the addresses in the code it gave you. ^^ )
Hope that helps - and happy New Year!
Toby