When are we supposed to our medical and background check

Me and my wife are employed US residents & Indian citizens. We received the ITA little less than a month ago and our deadline to accept the invitation is on May 20th. We have already received the FBI clearance certificate and still waiting on the PCC from India. We have our medical check-up scheduled for this week. However, I do not see an option to submit documents for these while filling the details for ITA. Are we supposed to do these checks now or after submit the ITA?

Once you fill in all the details, you will be taken to the page where you can submit all the documents.