Hi @shafiq12
That is great to hear that you are intrested in working with us. 
And this will be the talk thread for the project.
We are (Me an @batbrain7) currently focusing on Visits , Location , Encounter , And Patient Resource types.
The next resources we will work on will be here
As it shows u can pick up concepts resource type and move forward.It will be great.
Resources for u to refer
OpenMRS API docs :- https://psbrandt.io/openmrs-contrib-apidocs/
OpenMRS Swagger documentation:- https://qa-refapp.openmrs.org/openmrs/module/webservices/rest/apiDocs.htm
OpenMRS Data model :- https://docs.openmrs.org/datamodel/
And u can intreact with the endpoints and get how there used by refering the OpenMRS Reference application server hosted here
First we will be working on mark down documentation.One markdown file for one resource.
You can find the repository that we are working here .
Fork it and make sure to send a PR when u are finished working on a resource.And let know if there are any problem for u to get started
Thank you Ayesh