I had paid the fees yesterday so when my choice filling will start

You can fill your chances after your documents are all verified. It takes one day to verify your documents. Last date to fill your choices is 26th June.

If you want any help regarding choice filling to know which colleges nd branches you can get based on your rank you can use below college predictor

http://www.engineering.careers360.com/upsee-college-predictor

Good Luck!!