If you're a group admin, you can invite people to join a group by sharing a link with them. To share a group invite link:
Go to the WhatsApp group chat, then tap the group subject.
Alternatively, tap and hold the group in the CHATS tab. Then tap More options > Group info.
Tap Invite via link.
Choose Send link via WhatsApp, Copy link, Share link via another app, or QR code.
If sending via WhatsApp, search for or select contacts, then tap Send.
The admin can Reset link at any time to make the previous invite link invalid and create a new link.
Note: Any WhatsApp user you share an invite link with can join the group, so only use this feature with trusted individuals. It’s possible for someone to forward the link to other people, who could then join the group without additional approval from the group admin.