The rule to change voice from active voice to passive voice in present continuous tense – 

Active VoicePassive Voice
Subject + Am/is/are + Verb + ing +Object  Object + Am/is/ are + Being + verb [past participle] +by/with/to +Object 

Examples

Active VoicePassive Voice
Nandita is reading a bookA book is being read by Nandita.
Supriya is feeding the cows.The cows are being fed by Supriya.
Aunt is cleaning the house.The house is being cleaned by aunt.
He is filling the glass with mango juice.The glass is being filled with mango juice by him.
The girl is writing an essay.An essay is being written by the girl.
I am learning yoga.Yoga is being learned by me.
The rain water is filling up the ponds.The ponds are being filled up with waters.
The police is investigating a serious crime.A serious crime is being investigated by the police.
I am inviting you to my home.You are being invited to my home by me.
Mother is baking cookies for me.Cookies for me is being baked by mother.