Go to Clients, and click the red circle at the bottom right of the screen. A window for quickly adding a candidate will pop up on the right . Fill in all the required information and click Create:
You can also open a whole empty profile of a new client and add more information. To do so go to 'CRM'>'Clients', hover on the red plus icon in the right bottom corner and click on the icon above 'Add client in a new tab':
Fill in all the required information and optionally other information as well and click 'Save'.