HI ,

You have already filled the application right? only payment is left to be done. Its pretty easy to do the payment. But Im afraid the portal is already closed , because online submission along with the late fee was on 31 march 2019. Exam is held between may 2nd and May 3rd 2019. For MHT CET , the payment portal is closed as exam is another week away.

You should have done the payment before. Im sorry but I dont think you can pay now, as MHT CET for engineering.
I dont think they would allow you , but you can contact them once for any alternatives here -

https://mhtcet2019.mahaonline.gov.in/

Hope this helped,

You can get in touch for any further queries,

All the best.