Tap on the WhatsApp Icon.
Make Sure That, You Are on the Chats Tab.
Tap on Your “Group Chat”.
Tap the Subject of the Group.
This is the Name of the Group at the Top of the Chat.
Tap On “Group Description”.
Enter a New Description.
Tap Ok to Save it.
As You Can See, Group Description Has Been Changed.
This is How You Can Change WhatsApp Group Description on an Android Device.