Dear Sohel.

     The first thing you should do is to create a repository of stock photographs and videos. Upload your work in as many places as possible. Keep practicing and be persistent. Network and get  involved in groups which has been doing similar work.  Upload your work in as many places as possible. Grab any chance that comes your way. Collaborate with some one already established by either assisting or getting mentored.Work with journalist and participate in as many contests as possible. This way the kind of work you are looking for will surely come your way.

Good luck !