Terrarium plants can survive on the moisture inside the glass for a while, but they still need some water to thrive. The closed environment of a terrarium creates a self-sustaining ecosystem, where plants release moisture into the air and it condenses back onto the plants, but this cycle can be disrupted if the terrarium is too dry or too hot. I'd recommend checking the terrarium regularly and watering sparingly, as overwatering can be detrimental. A good rule of thumb is to water only when the soil feels dry to the touch, usually every 1-3 months, depending on the plants and the environment.
