Make sure that your house is not letting in a fresh supply of rats. Grill your ground floor windows with steel mesh (not plastic netlon types which can be chewed through), seal off any cracks on walls, drains, close all doors that connect to the outside of house before dusk, keep all kitchen trash in sealed containers, always store food safely after meals, and keep floor swept after each meal especially when there are little children who would spill food.
Start off with a physical hunt for rats and destroy all pests you find. If you do not have peace about killing rats, do hire someone to take care of the matter. It is not right to transfer the pests from your place to another by just letting them loose in another area.
You can capture and kill rats in your house in two ways. One is to use commercially available rat poison. Another is using traps.
Rat poison is effective when you do not have too many places where rats hide. If you can reach all parts of your house easily, and move furniture and other items easily, then this is the best option. Rats eat and run around a bit before they die in some remote corner where you may not have access. Then it becomes a smelly affair until you find where it died. If you are not in a position to do that, then go for traps.
Traps are also okay to use, but you will need to kill the captured ones, and set trap repeatedly over a period of time.
Make sure you place poison and trap where little children cannot reach. Rat poison is deadly.
Other options are available. You may use ultrasonic repellants which emit sound at a frequency that is outside human hearing range, but its effectiveness in households is not known. You may hire professional services if you are sure about the integrity of the people involved. Some agencies are known to clear out one pest but quietly introduce another pest to your home, so their business is sustained.
Another method I have heard is by using some sort of adhesive or sticky tape where the rat gets stuck by the strong glue. I am not sure if it is available or what else is involved regarding that.
An overall clean environment discourages many pests.