Attaching a wheel to a metal rod (axle)?
You may notice that the wheel is described as being suitable for carts, hand trucks, etc. and is not designed as a drive wheel. If your loads are not excessive, you may get away with powering the wheel.

One method is to cut a slot in the flange of the wheel at the axle. Your drive axle would then have to be powered by the motor and the portion of the axle that engages the wheel would have a hole drilled and a pin used to engage the wheel.

Another method would be to create a mounting for a pulley or gear. A pulley will be easier for alignment purposes. Drill a series of holes in the wheel (think numbers on a clock) and add spacers and bolts to match the pulley. Drive the pulley with another one mounted to the motor. This method would not require the axle to be rotating.

Along this same line of thought, one can use a bicycle sprocket mounted in a similar manner to the pulley and replace the belt with a bicycle chain.

Gears are not as easily installed as alignment is critical, while chains and belts are more forgiving when using the TLAR method (That Looks About Right) for attaching the mechanisms.

Belts and chains also provide for gearing adjustment. Perhaps you need more power and less speed. Use a small gear/pulley on the motor and a larger one on the wheel. For the reverse, more speed, make the wheel pulley smaller and/or the motor pulley larger. A small change in either will make a substantial difference.