How to add a skin to sides - club 5983

Hi Club 5983 here. We're redesigning our webpage and we want to add a jpg picture of sand and sea and skin the sides of the homepage.
It doesn't give us an option to upload a picture so how can we do it? We did it on our meetup page and we want to brand the homepage like that.
Any advice is appreciated.

Best -
Marlene
VPPR 5983

As usual, you guys are ahead of me... Take a look at the back ground on my development website:

otbp.toastmastersclubs.org (other backgrounds will be possible, included uploaded ones)


So... please be patient. Not doable yet, but likely in the not too distant future. (being intentionally vague)