You literally put the money + a piece of paper with your account number into an envelope and mail it to them

Fellow Zer here, my elective IT class had grading done depending on how well you could use the computer:

‘A’ if you could do everything perfectly well, ‘B’ if you needed some help from the instructor, ‘C’ if you needed a lot of help, ‘D’ if you couldn’t even get past the login screen on the windows machine.

We had a lot of people who got a pity ‘C-’