@krishnaverma is right - first you shall think of the traffic source, a product and the ways to promote it, ways to make money on it. In this case you started without any plan

Now think of your points of difference. There are a lot of URL shortners available, how are you different from them, what's your advantage?
This advantage is something you can promote after to online marketers and everyone who may need the link. For instance - you could even describe your product on affiliate marketing forums (like BHW) in a special section for companies, place your ads on related websites, etc.
You can also create a tutorial on how to use your link shortner, post it on YouTube and try to get as many people as possible to see that video. Of course, you'd need to insert the links to your tool, make a good description, etc.
There are many ways, try to explore the ones that seem more interesting.