HI Jez, and welcome - both to the forum and to the world of motorhoming!
First fo all, you need to get familiar with your vehicle's equipment, and make sure you know how to work it all.
When you say it's got nothing with it, let's start by making everything work. So you'll need a mains hook-up lead. Any fittings which need mains (ie anything with a domestic-type plug!) will ONLY work if you're connected to the mains. There will be a blue connector on the outside of the van somewhere, and you need a cable (usually orange) with blue plugs each end, to connect that to the mains supply on a campsite. To get it all working you're at home, you'll want an adaptor withy a domestic plug on the end.
You'll also need a gas supply (probably a Calor Gas cylinder or similar). If there's an empty one on board, you take it to a dealer to exchange for a full one - but take your credit card!
Since pitches on campsites aren't always completely level, most people find it useful to carry a pair of "levelling ramps." With a bit of common sense you can work out which wheels to put them under, depending which way you're tilting!
Beyond that, it's down to you, and what you feel you need with you to live in the van. Cutlery, crockery and kitchen utensils; your preferred type of bedding; maybe some tools if you 're up for minor running repairs, certainly a roll of "gaffa-tape" ...
I could write a book, but fortunately someone already has. There's a "Haynes Manual" (yes, the people who do those workshop manuals for nearly every model of car!) about motorcaravans in general. you can byu it at places like Halfords, and lots of people find it really helpful.
Keep asking specific questions on here, and there will always be someone who can give you an answer - if you're lucky you might get several different answers to choose from! And before long, you'll be giving advice to other newcomers.
I look forward to hearing more from you!
(Oh, and I've used my magical powers to "upgrade" you, so you won't have to copy those annoying squiggly letters anymore).