The battery in your TV in a Card is rechargeable and your card has a mini USB port for this purpose.
To recharge the battery, simply connect the card to any USB port on a PC or Mac, which is capable of charging external devices. (Most USB ports on recent computers can do this)
Where provided, you can use the TV in a Card mini USB cable, with your TV in a Card. Alternatively, you can use any standard USB to mini USB cable.
You can also use this cable to connect to a USB charger to recharge the cards more quickly.
Please ensure the charger has a 5v output. Higher voltages will damage the cards.