Composting

Im just about to start my own vegetable patch and want to grow some fruit trees and wanted to make sure I was on the right path as regards composting. I've made up a a few bins from wood I had lying round. I just got a few fence posts which I've driven into ground and screwed the wood to it giving me three bins so I can leave one to rot as the others fill. I used some wood stain on this wood to try to make it last a little longer. Should I put anything on the ground in these bins or just start filling them on the ground? Do the bins need covered? Or can I leave them open to the elements.

The site needs cleared and currently has a large number of nettles growing on it. I was going to make nettle tea with these.

The garden has a big lawn and a quite a few mature trees. The lawn cuttings can go into the main compost bins and I understand that leaves should be kept separately in plastic bags with holes as they take longer to rot.

Uncooked food waste, shredded paper, cardboard and any other garden waste can go on the main bins.

Im not sure if rats would be a problem but one of these has been left at the house - Compost Tumbler 200L - Tesco.Direct If I put cooked food waste in here and place it at the far end of the field then vermin might not be a problem? Once it had rotted a bit i could mix it into the main bins.

Im sure there's other things Im forgetting but I've grown anything before or even looked after a garden so it's nice to have reassurance you're on the right lines!

Many thanks.