Hello
I am new to this framework and I am in a position to modify a silverstripe website to add a new page which make use of the data from DB. What is the best way to do that? Can I make a page inside admin and add content from database?

I'd go through all the http://www.silverstripe.org/learn/lessons/

Thanks for your intention to help, but that is the first thing I do when come in contact with something new. I am trying to add a new page in /mysite/code/pages and it says page not found when I am trying to access it. I've tried a new controller also with the same result. I've even tried to add a new action to an existing page and it didn't worked.

You are welcome, unfortunately I'm not sure that you have followed all the lessons. The lessons very clearly cover creating pages that include content from the database.

As you have not posted any code and asked "please help me fix my code" it's not easy to directly help... I could post an example yet the lessons are of a very high quality and I wouldn't better them.

If you want a more specific answer then please paste your code and specific error.

Be Well :)