There are several ways to integrate Tokbox, depending on the functionality the client is interested in.
For any approach, you'll first need to:
Ask the client to sign up for an account here.
Ask the client to add you to their team:
Account Settings > User List > Add user > Developer permission
Accept the invite and log in
Create a project
Then the other steps depend on the approach chosen.
Select the option "video chat embed" upon creating the project
Specify the website URL (note: you can only specify one)
Copy the iframe code
Paste it into your Bubble application in an HTML element
Adjust width, height and scrolling (see example below)
Make sure the room parameter is unique for each video chat users will launch
Not tested yet.