The water pump is leaking.
If the water pump is leaking, then it will need to be replaced. During water pump replacement, it is recommended that the timing belt also be replaced, since it needs to be removed while the water pump is being replaced.
The cooling system needs to be pressure tested, to ensure you have no other leaks, and bled, once it is filled. Never attempt to check the cooling system when the engine is hot, or the cooling system is pressurized, or serious injury can occur. You may want to enlist the help of a mechanic, such as one from YourMechanic, who will have the tools and expertise to ensure correct replacement of the water pump, and set the engine timing correctly.