Hi @dkayiwa,
here is the link to document: https://wiki.openmrs.org/display/docs/Registration+App+Configuration
regards
@hpardess, @kimkuere Iāve been struggling with the same thing, i had a personAttribute with a foreign key to a concept but couldnāt get it as a dropdown that retrieves concepts the personattribute is related to. Finally iāve just decided to extend the registrationapp on my own and add there personAttributeWithConcept field. I hope this is what you looking for here it is https://github.com/salta-kozbagarova/openmrs-module-registrationapp .
@saltanat if this is functionality which did not exist, did you consider raising a pull request? That way, you do not have to go through the pain of maintaining your own module. 
just done that
Yes i mean a pull request for that repository. You would need to first create a ticket: https://wiki.openmrs.org/display/docs/Tickets And then take a look at these tips to know what pull requests require before they can be reviewed and merged: https://wiki.openmrs.org/display/docs/Pull+Request+Tips
why canāt i find my repository in the drop down list of forks on creating pull request page? Do i do anything wrong. In the openmrs modulesā repository i go to New pull request but there in the list of forks i can see just static 30 or more repositories, and canāt find mine.
oh, thatās it, iāve forgotten about it! Thanks!
Have you committed your code to the main module? Please share the issue ticket #