How can you tell a normal person (i.e. your mom, grand mom, your little brother) how was the first program was written? They ask this question a lot and I really can't give an answer they can understand.
It depends on how you define things. The first computers were programmed largely by rearranging patch-cords. Only (a little) later was memory added to produce stored-memory computers. The first programs for these were written by turning switches on or off to set 0's or 1's for a word, then (when they were all set to the right values) toggling another switch to "push" that word into memory, and setting the "current location" counter to the next memory address.
The same basic idea continued to be used for the initial boot program for quite a while after computers had memory -- e.g., once upon a time I wrote code for a Control Data mainframe that had a set of switches to toggle in the boot program (though in this case, they were on an auxiliary computer called a "PPU"). I also (again, long ago) booted a rather oddball variant of a DEC PDP-8 by toggling the boot code in on front-panel switches (and even though that was decades ago, the computer in question was already obsolete at the time).