If your task is set up to use Codes (you can check that Use Codes is set to 'Yes' in Settings - the 'cog' icon), then you will be able to upload candidate details to your task.
Normally this will be via the CSV Upload facility. However, if you need to add a small number of candidate details after the main CSV upload (or if you have a very small cohort), then you can add the details manually using the 'Add Candidate' button.
When you click into your task from the task list and then click on Populate, generate, download & print coded sheets, it will take you to the Candidates page:
Click on the 'Add Candidate' button (the 'plus' sign) and you should see this screen:
Enter the candidate's details as appropriate, and then press the 'Update' button:
You will now see the new candidate added to your Candidates table:
Repeat as necessary, if you have more than one candidate's details to add.