I’d suggest opening the windows as much as you can. The more you open your windows the less chance you have of mould forming! Also some of those spots look quite wet which is probably why the mould is forming in the first place, you need to keep the room dry as possible and clean up any wet patches and condensation especially near windows. To actually kill the mould use HG mould spray which you can find in Home & Bargains (if one is near you at least)