You have three options:
1. As explained in this instruction.
2. Go to the candidate profile, hover above the red circle at the bottom right and click Send message to candidate:
A window with a message will pop up. Click the Select template icon displayed under the message, just next to the Send button, and select a template from the list. If there are personalized elements in the message (e.g. the recruitment that the message is connected to or the name of the client this particular recruitment is for), you will be asked to choose them:
3. Go to Settings -> Recruitment processes to enable the option to display the option Send email to candidate each time when you move the candidate to the next stage (when you click the message, a window with a message will pop up). Select the process from the list and click on the transition between stages:
...then in the new window give the transition a name and choose an action that Traffit has to take. Next, click Add and Save: