Compost works best if there is some drainage and some ventilation (or occasional turning/mixing) otherwise it becomes soggy, anaerobic and smelly.
I would start by making some large holes in the base and sitting it on the ground. That way it can drain and the soil bacteria will make contact with the composting materia and start the decomposition process.
The rest is not rocket science, although there are some complicated 'recipe' around - fine if you are doing it all at once but most people make compost as they have the ingredients. Just layer any thing organic - chook poop, green stuff -lawn cuttings (only thin layer) weeds, vege scraps and dry brown stuff -leaves, small sticks, straw, news paper, cardboard, as you have it. Don't add meat. Keep the whole lot moist but not wet and occasionally fork it over if you can be bothered. A hand full of garden lime ocassionally will help control any smell and help the composting process
It is ready to use when it looks like dark soil or has a worm population. The bottom layers will be ready first so consider cutting the whole base out so that you can lift the bin off.