Just take the printout of page 53(Annexure 8) from business rules pdf from josaa website and take the print out.

Go to any government hospital and ask them for check ups written in format of medical certificate in JOSAA's BUSINESS RULES.

Plz note that you have to go only in gov hospital otherwise your certificate would be invalid.

Feel free to ask me in the comment box if you are having any further doubts

hope you find it helpful 

Good Luck!