about order 6 rule 17 cpc

sir I am party in person and I filed writ petition. In full cause list there are 3 govt offices and one private person. petition is in the admission stage and only court show cause notices issued to govt respondents for admission and I served personal notice to private person. case posted after 40 days. In the mean time I found that for the same cause of action against other private person and I want to add that another private person to that petition as respondent no 5. can It be done through filing IA as per order 6 rule 17 CPC. please tell me the procedure regarding filing such IA. Thank you