To set up a load/unload route, you first need to left click on a donkey to select it:


Next, you will want to hold down the shift key while performing ALL of the following.

First, with the donkey selected, press either the pickup or dropoff buttons (For this guide I'll assume you pressed the pickup button, but if you hit the dropoff button, just perform a pickup later on rather than a dropoff).


After than, click where you want to pick up from. Here, I am picking up from a water well:


Next, click the dropoff button.


And finally, click where you wish to drop off the resources.


In this example, after I click that last drop off, I have created a load/unload route with my selected donkey from a water well (pickup side) to an omni t1 bulk storage (dropoff side). To deselect the donkey, you can just left click on an empty space to get rid of the pickup/dropoff command, then left click on that same empty space again to actually deselect the donkey.

You can mess around with this command order to accomplish other things. For example, you could have selected two or more donkeys instead of one. Then you would have created a load/unload route with all of the selected donkeys.

As a side note, if more than two donkeys are consistently extracting from a single resource extractor, you are wasting effort since according to one of the developers on the Industrial Annihilation discord, a resource extractor will be saturated once two of its connectors are in use. Apparently they extract at two resource units per second from what I was told.