What you need from Meta
A Meta business portfolio, an app of type Business with the WhatsApp product added, and a phone number on it that is not already used in the WhatsApp or WhatsApp Business app. Meta's test number works for trying it out, but it only messages the recipients you list.
Four values come out of Meta: the phone number ID and the WhatsApp Business Account ID from WhatsApp › API Setup, a permanent access token for a system user, and the app secret from App settings › Basic. The temporary token on the API Setup page expires within a day; use a system user's token instead.
Create a system user
In Business settings › Users › System users, add an admin system user and give it the app and the WhatsApp account, with full control.
Generate its token
Pick the app, set the token to never expire, and tick whatsapp_business_messaging and whatsapp_business_management.
Connect in Wiredesk
Paste the four values into Channels → WhatsApp on the agent and click Connect. Meta checks them before anything is saved.
Point the webhook at Wiredesk
In the Meta app, WhatsApp › Configuration: paste the callback URL and verify token from the channel page, click Verify and save, then subscribe to the messages field.
Switch it on and send a test
Turn on Answer WhatsApp messages, then message the number from your own phone.
The 24-hour window
WhatsApp lets a business write freely to a customer only within 24 hours of that customer's last message. The agent is always inside it, because it is answering a message that just arrived.
A reply from your team is different: it can come later. The conversation page says whether the window is still open and until when. Once it has closed, the reply box tells you so and nothing is sent; the window opens again when the customer writes.
When a person needs to step in
Handover works as it does for chat. The agent flags the conversation, you are notified, and whoever replies from the conversation page takes it over: the reply goes out on WhatsApp from the same number and the agent stays quiet. It picks up again after half an hour of silence from that person.
If nobody replies within ten minutes, the agent tells the customer on WhatsApp that nobody is free and carries on.