Firstly, how long has it been laid down? 2ndly was the soil underneath prepared beforehand? 3rdly if it was very recently this weather will give the roots time to get established, 4thly did you pull any dandelions and deep rooted weeds out when laying? So, if it`s been down for a few months get some Lawn Feed & Weed and follow the instructions on the label. You know it makes sense. lol
During at least the first season with your new lawn , assuming of course that it has been laid properly, you will have your work cut out (pun not intended!!) to keep the growth under control , because of the root pruning action when the turf was lifted to be put in your garden. Don't feed it because it isn't necessary.