Hi I want to know if someone have already developed an application to share this experience like how you start .

There are many schools of thought on this subject....basically..

1st you have to figure out your concept...what does your application do for it's users ?

What type of business/service do you want to create ?

Do you have the coding skills to actually build the software/website that you are thinking of ?

2ndly ..You must research if your concept currently exists ..it may not exist exactly as you see it in your mind..but may exist in a form very nearly to what you have envisioned for your application , this will tell you if there are competitors and what type of product they are offering .

You can check some of these sites to see if there are similar products available https://github.com/mmccaff/PlacesToPostYourStartup

3rd ..What features will your application need to be successful ..some features can be found looking through open source libraries and are a great source of ideas about features and capabilities that you can add to your application to improve it for your users .

These are free..however if you use them you should give credit to the creator , this is usually done in the About Us page on you site or somewhere in your software info .

These are the ones I use..they include the source code which you can modify for your own needs or projects .
https://codepen.io/

https://threejs.org/examples/
( click on some examples in the menu on the left )

https://github.com/d3/d3/wiki/Gallery

You will find great advice here..This community has helped me improve so much and has given me many resources that will help my business grow .

So tell us about the application concept . ?

Welcome, Leila. Mind sharing more about the project application?