Once you have sufficient privilege, you can create a new chat room at chat.stackexchange.com/rooms/new as shown below.
If you don't have enough privilege or do not want to create a new chat room, use one of the existing Hinduism.SE's chat rooms to chat. Here's the link to all Hinduism.SE chat rooms.
When creating a new chat room, however, you need to make sure you change the Related Site (parent site) for the chat room to Hinduism.SE or else the chat will be created on Stack Overflow and other Hinduism.SE users will not be able to locate your chat easily.
If you do forget changing the site to Hinduism.SE or you've accidentally selected a wrong site, there is no easy way to fix it. You need one of the Stack Overflow moderators to get involved++ to change the parent site for the chat. But this will not stop you from chatting with other users.
How to create a new chat room specific to Hinduism.SE:
++ If you need one of the Stack Overflow moderators to re-link your chat to Hinduism.SE, just write a comment in the chat and flag that comment for moderator attention. Explain the problem and one of the SO mods can move it under Hinduism.SE. It appears that Hinduism.SE moderators cannot fix this issue themselves without some help from SO mods. But you can always ping one of the Hinduism.SE mods and they'd be happy to communicate with an SO mod and get it fixed.