I don't know how does it work for the first time if one of my parents applying for a visa to come to the US. I think they get interviewed. I have been struggling with health issues, however I heard giving that reason is not a good idea. Any suggestions how to prep and bring the person as soon as possible ( I heard the wait for interviews are long either)? Thanks!

You can apply from this website https://www.ustraveldocs.com/np/
You will have to create an account and then follow the steps to apply for a visa.
I think you will see options for urgent visa too. Good luck

Thank you for the response.