If a student is given credit for a previous class, you need to first, set up that class in your courses.
After that, you can assign this course from prior to the program, maybe even from a different school, to satisfy your apprenticeship's related instruction requirement.
You can either assign the course to satisfy a current related instruction requirement from your program (See here)
Create a new requirement and assign the course that way. (See here)
After, you can immediately approve the course.