3M hadn't gotten busy and invented the ubiquitous self adhesive sticker (at least I suppose it was 3M!) so you had to cut the pictures out, lick them yourself and stick them into place.
Somewhat more skill-teaching then than today's method!
Construction Books: Installment No.1
We have a number of kinds of these; here's one!
A sticker books from the 1930s, by Hank Hart
Stickers and destination picture from "Pasting without Paste Playbook" by Hank Hart