Endorse what Old Salt is saying. Just water it but don't overdo the water. Little and often is much more beneficial than a flood once a week.
If you have any bare patches then mix a few seeds with a handful of top soil, sprinkle it on and tamp down then give it a gentle water. Avoid walkingon the lawn as much as possible and try to use a sprinkler to save dragging a hose over it. I have been watering mine once early in the morning, again around lunch time then a final one early evening. Have your hose on the shower setting and move it fairly quickly from left to right then backwards going up and down. Move on to the next section and repeat. Your aim is to get the surface quite damp but not sopping wet. This will allow the water to penetrate the soil rather than run off the hardened surface. In a short time, (maybe a week to 10 days), with some sunshine your lawn will start to look more like its normal self.