Actually, you need to define your target audience before starting a new business. Otherwise, how will you know if anyone needs your product or service?
Frankly speaking, I doubt if you're serious about this thread.
Start a campaign to draw your audience to you. Use social media like Facebook, Instagram, Twiiter, just to name a few. You can create ads on all three to go after your audience. If you don't want to create ads, you can do it the organic way but that will take work. Instagram is good for the organic approach because you can hone in on your audience using hash tag searches and posting with targeted hash tags. Hash tags are very powerful with Instagram and should always be used.
Your website should have opt in options to get people's emails so that you can create email lists.
Not knowing what it is your business offers, I would say that actively updating your site would be ideal. This is what a blog is good for.
To summarize, attract people to your site via social media, get them interested in your goods or services via a blog, and have them opt in to build your email list.
It will take time, there is no magic bullet to attract people to your site so work will be involved. You can't just start an online business with a website and expect everyone to know about it.
Target audience for your business, many sources available. Basic things to find your target audience is,
Determine what needs your product fulfills
Who is most likely to be interested in the values your product or service offers
Gather survey data to identify potential markets
Look to your own network for data