I am looking at this product, and wondering if I can install wheels on them.
There is no "one-step" way to install casters on these types of shelves. You would have to build a base, or affix them to something like a mobile power tool base. In general this would be a lot of work for a potentially dangerous rolling shelf.
You would be better off finding a wire-type shelving unit, which are often built either with casters, or slots for casters in each post. The cheaper the model, the more risk of collapse, so if you are planning on putting anything heavy on it, I recommend finding a restaurant model, which are built to handle pretty heavy loads.
Those shelves require a solid base. So you'd have to build a solid base (plywood could work) and attach casters to those. Then attach the shelf to that. However, you still have the issue of moving said shelves. Those shelves are designed primarily for vertical loads and tend to not handle lateral loads well at all...which would be the case when you push or pull against them to move them.
As such, I'd strongly suggest not using those types of shelves if you want them on wheels. Instead, use wire racks (typically used in kitchens) that are designed specifically for casters and handling being pulled and pushed around:
You can find these in most big-box stores. Sam's Club and Costco often sell them.
I have both these types of shelves and the ones you refer to. There is a price difference, but it's not huge and I much prefer the wire shelves. They're also much more durable in terms of disassembly and reassembly when moving.
You could drill through the bottom shelf and attach some casters and then reinforce the sides with some wood or other means. This should make it durable enough to roll around somewhat.
I guess the other option would be to mount a support below the bottom shelf, screwed on through the corner holes, and attach the casters to that. Then again attached some siding if needed. Same concept, just a different way to get the wheels on there.
As the others said though, this setup might not be the best choice for rolling around. Even if you can't get something else with wheels, there would be better choices that would be easier to attach to.