You need to host the project as the instructions say βWhen you are done, make sure a working demo of your project is hosted somewhere public. Then submit the URL to it in the Solution Link field.β
There are several free options online you can find to host the project. Have you added your code to github? Of the hosting options I have used you will need your project on github for the hosting websites to access
Some free options to host that I can think off the top of my head are netlify and vercel.