Turning website chat on
Switch website chat on from Channels and get your chat's code.
Updated
Open Channels and press Set up on the Website chat card. The page reads "Chat on your website." and reminds you that website chat uses one of your plan's channel slots. Press Turn on website chat.
If every channel slot is already in use, the page says "Your plan's channel slots are all in use. Disconnect a channel or change your plan to add website chat." with a View plan link. Disconnect a channel, or move to a plan with more channels, then try again.
Turning it on gives your website chat its own key, which is part of the code you paste (see Installing the chat on your website). The key never changes, even if you turn website chat off and on again.
The chat's name starts as your business name and its greeting as "Hi! How can we help you today?". You can change both under Look.