A tea warmer needs a clear safe space
Before lighting a tealight, check the pot, the support and everything around them. A cosy-looking setup still contains an open flame.

Compatibility comes before appearance
A pot fitting neatly onto a warmer does not prove that it is suitable for direct heat from a tealight. Check the instructions for both pieces. A vessel intended only to hold a hot drink may not be designed for concentrated heat underneath. Do not improvise with a decorative bowl, an unknown glass pot or a cracked vessel. The support must hold the pot steadily, with the required clearance and ventilation. Use only the candle type and number specified by the warmer's manufacturer. Adding a second candle because the tea seems cool changes the conditions of use rather than providing a harmless adjustment.
Clear the space before lighting
Place the warmer on a stable, level, heat-resistant surface, away from curtains, paper, dried decorations and anything that could fall across the flame. A fabric tea cosy does not belong over a lit warmer. Keep the setup out of the reach of children and pets, and where sleeves will not brush it as people pass dishes around the table. Light the candle only when you can remain nearby and attend to it. Never leave it burning when you leave the room or go to sleep. If the arrangement feels cramped, choose another way to serve the tea rather than trying to squeeze a flame into the available gap.
Watch the drink as well as the candle
Remove the tea leaves before holding the finished drink warm, unless a specific preparation intentionally keeps them in the vessel. Otherwise continued extraction can change the flavour while you are concentrating on the warmer. Follow the pot's guidance on minimum contents and never let it heat empty. Extinguish the candle before the remaining tea becomes too low, and let the equipment cool before moving or cleaning it. Do not pour cold water into a hot vessel to speed the process. If the purpose is simply to enjoy another cup later, a suitable insulated serving pot avoids an open flame altogether. A warmer should be an intentional choice for a supervised tea table, not an appliance you forget is running in the background.