You will need OpenMRS running either through standalone or developer version.
1)Download/clone Open web app module's code from here - https://github.com/sunbiz/openmrs-module-owa
2)Refer to basic app mentioned here - https://github.com/namratanehete/owabasicapp
3)Create new app based on this basic app.
4)Create html page with textfield and search button to search concept.
5)Use Get operation of Rest call to get concept - Refer concepts section of https://wiki.openmrs.org/display/docs/Sample+REST+calls
6)Display response in html page.
7) Make a github pull request.