Try opening the website mentioned on a laptop or desktop for easier processing 

Dear aspirant, 

Don't panic, stay calm. I'm providing you the link of payment of processing fee. You have to pay the fee online either by the use of net banking or by using cards.

After your payment success you have to take the print out of it by clicking on the print receipt option and you have to bring this print out at the time of certificate verification along with other documents.

Here is the link. 

https://apicet.nic.in/payFeeOnline.aspx

GOOD LUCK.