You can launch a Journey in two ways: from the Launcher or from a Tip.
Do it from a Tip, you need to open the Tip dialog in the editor and select the dialog bubble icon:
A list of the available Journeys for that site will appear:
Select the Journey you wish. A colorful link will appear:
There are 3 possible colors for the link in the editor, as specified on the left, and how they appear to the end user, on the right:
The red link does not appear to the end user on the live site because the Journey linked is not available.
If you have a yellow link in the editor, it will go green as soon as you mark that given Journey with the "Send to Publication" status, by clicking on the button shown below. The yellow link is to make you aware that the Journey concerned is under review and currently not live.