B2- visitor visa extension for mother

[madurirv]

I am filing the visitor visa extension for my mother(B2) . I read it in USCIS that we have to file the i 539 form atleast before 45 days of i94 expiration and it can be efiled.

I dont see anywhere that we can efile it. Can someone let me know if we can file it online/efile by providing the correct url.

 

Also can someone share the correct supporting documents for it along the filing fees.

 

thanks for your help in advance!!a