Thank you Scotland for this advice and photograph. Please use a 6.5mm and then 7.5 mm drill bit. Do not tighten nuts too tightly. Please do not use glue on these items.
The nuts are provided with the set. You drill first with the 6.5 mm to make the whole and make it bigger with the next drill but up. Clean off the excess plastic ‘twirls’ and wipe clean. Gently press the threaded ‘bolt piece’ through the lid and screw the nut on till tight. Do not glue or too much force. Clean after doing in a steriliser. If you don’t feel confident with a drill ask someone who does.