If a candidate does not apply through an Internal Job Posting, you can mark them as an Internal Applicant by following these steps: 

1. In Recruiting, navigate to the candidate's record and click the blue icon (). The candidate's Info screen appears.
2. In the Candidate Info section, in the Set Source/Referrer field, select Internal Applicant. 
3. Click Save. When a candidate is marked as an Internal Applicant, their record is invisible to all Standard Users unless the user is assigned to the correct job. This assumes the feature Hide Internal Candidates from Standard Users is turned On in Admin > Company Settings > Candidate Hiding.