Airport Aruba.com/map has the best explanation for the process that I've found.
https://www.airportaruba.com/map
Look at the legend for "US Bound Passengers" then follow the purple path on the map, beginning at "US Departures" building on the bottom right. Note that the US Departure area is very short walk from the onsite rental car agencies. Assuming you're renting a car, it would undoubtedly be easier for you to be dropped off with your bags in front of the building and then you can wait for the driver to join you.
In any event, in the building marked "US Departures" you will have your luggage weighed and checked-in at your airline's counter, just as you do in the States. You will retrieve all the checked bags, and re-check them in, but not until in step D. For steps A, B, and C. it'll be just you and your carry-on items. Steps A, B, and C are Aruba's immigration and their equivalent of TSA check. ALL departing passengers (including non-US bound passengers) must go through steps A, B and C.
For US bound passengers, you then proceed to the US Customs pre-clearance area. Not many international airports offer this service, and while it is a minor and time-consuming PITA, it saves you from having to go through US Customs once you arrive in the States. The downside is that it requires you to retrieve your checked bags (which at this point have passed Aruba's screening) and haul them (either by hand or by cart) through the US Customs area (steps D,E, and F).
In Step D, you retrieve your checked bags from the designated carousel. I assume in this area they will once again provide luggage carts for those who need them, because you do not surrender them again until you've gone past Customs.
In Step E, you get in the line to be interviewed by US immigration officials, OR if you have Global Entry, you can bypass the line and use a kiosk.
In Step G, you load your checked bags back onto a conveyor belt. From this point forward, you should only have your carry-on items, including any Duty Free bags.
In Step H, you have to queue up once again, this time for the US TSA screening (where they say they honor TSA pre-check, but that wasn't my experience).
After this, you can proceed up the escalator the your gate and to the bars where you can celebrate making it through!
In a few years, they've promised to streamline this procedure so that you don't have to go through two separate checks. But this is it for now.