Don’t put any meat/fish, cooked or raw. No cooked or processed food. You can put any raw veg or fruit waste, egg shells, tea leaves/coffee grounds (tea bags in theory though they do have a tiny amount of plastic), some delivered magazines now have compostable covers, shredded paper and cardboard, hair e. g. from your hairbrush etc. A mix of layers is good, I. e. some grass then kitchen waste, paper, before more grass. You can get a compost turner/stir-er online, can’t remember the website now, but it is important to somehow mix it round or turn it over to get air into it. Oh, I chuck some garden worms in mine every time I find a few, as they help to break it all down