Note, I never actually used punch cards, but they existed when I was in college. The user interface was like this:

1. You prepared you cards, offline using a punch machine.

2. You got a form from the computer center and filled it in with various details for your job.

3. You wrapped the form around your card deck, secured with a rubber band and placed the assembled package into a box/shelf in the entrance to said computer center.

4. You went about your business for a day or so.

5. You checked your pigeon hole outside the computer center, or perhaps your department mailbox.

6. Eventually your card deck would show up there, accompanied by a line printer (fanfold) output that was whatever your program printed when run.

There were more complex workflows allowing things like tape input/output where you'd specify the tape label either on the form or in the deck.

This is where "Job control language" (JCL) comes from -- a scripting language to facilitate running batch jobs. The precursor to Dockerfiles and Github Actions YAML.