It’s 100 times further than the Moon (3000 Earth diameters away) and been in that orbit for nearly a century.and 40 to 100 meters in diameter. And should continue in that orbit for several centuries to come

It’s in a rather unusual orbit. It is always in roughly the same part of the celestial sphere as seen from Earth, tracing out a big figure of eight in the sky.

Earth's first 'quasi-satellite' identified

That seems bizarre at first, but think it through. It’s in a one year orbit around the sun like Earth. If at some point it is between Earth and the sun, then half a year later, it’s going to be further away from the sun than Earth (has to have the same semimajor axis), and that makes it still in the same direction in space from the Earth.

So - it’s a bit strange to call it a moon since it’s always in the same direction from Earth. But on the other hand, each year it crosses the Earth to Sun line twice, so in that sense, it sort of is in an orbit around Earth, but only in a rotating co-ordinate system.

This shows its orbit though not so easy to follow what is going on as its orbit is so unusual, this is in a rotating frame so with Earth stationary and from this point of view it seems to “orbit” Earth. It’s inclination is not as huge as it seems in this video, it’s inclination is only a bit over 7 degrees so it is pretty much in the same plane as Earth’s orbit:

NASA announcement: Small Asteroid Is Earth's Constant Companion

Wikipedia article with more details (469219) 2016 HO3 and see also Surprise! Newfound Asteroid Is 'Quasi-Moon' of Earth

It’s about 5 km / sec delta v to get to it from Earth in an energy efficient orbit, and about 1 km / second to get back to Earth, relying on aerobraking in the Earth’s atmosphere. NHATS Object/Trajectory Details

Could we do anything useful with it? Assuming two metric tons per cubic meter for a very rough idea, and diameter 40 to 100 meters as they suggest, that would be . between 2.26 million tons and 8.38 million tons so it's a lot of material. By comparison a Stanford Torus requires 10 million tons. So you could do a fair bit with it, depending what it is made up of.

If it is an iron meteorite, you could use the second half of the Mond process, react the nickel with Carbon Monoxide in a big balloon warmed up enough in the sun to reach the temperature for nickel carbonyl gas of 50–60 °C and then convert back to the pure metal in 3D printers at 220–250 °C. Other metals can do the same but at higher temperatures .But we don't know what it is yet, could be a source of volatiles also. Might be useful in some way. If nothing else it could be useful for shielding.

If it has useful resources then you could supply them to LEO or to the Earth’s surface using that 1 km / sec return trajectory with aerobraking.

Or perhaps it is useful where it is at some point? Or just of scientific interest.

Also, I wonder if it could be the first of many smaller objects in similar orbits. At any time the Earth probably has at least one asteroid of diameter a meter orbiting it and probably many smaller ones, I wonder if it has a cloud of these more distant moons as well? Simulations Show Mini-Moons Orbiting Earth

See also: Robert Walker's answer to How can scientists be sure that asteroid 2016 HO3 won't ever hit the Earth?