Launching a new business can be tricky as you may be starting from a completely blank canvas. It may be that you are launching a new product or service that is not known so you will have to make people aware of who you are and what you are offering. Having a website is a great place to start, but if none knows you exist then they may not search for you or your products. Social media is a fantastic way to get your brand and products recognised. You can opt for the paid for advertising or you can choose to build up a following organically. If you decide to go down the organic route then you need to think about how you care going to get your posts seen. You may be able to advertise on some local groups but be aware as sometimes these groups have restrictions regarding advertising. You can also ask all your friends to share posts and links to your social media pages.
The best way to build up a following quickly is to offer a prize draw. Some many companies quickly gain hundreds of followers by running a giveaway competition in exchange for a share and like of their page / posts.