You tap an icon that looks like the outline of a rectangle with an arrow pointing up. Then you tap the name of the printer. Then you tap another rectangle with an up arrow and then tap the word "Print".
I may have got the precise steps wrong but it really is that abstruse to print something on a tablet. Never mind that mDNS/Bonjour has done its thing - the steps to actually indicate that you want to print is frankly weird.
What on earth is that box with an up arrow actually supposed to mean? Why does the interface switch from icons to text?