They should begin with a tunnel boring machine. You've got that impending micro nova event to contend with. The best place to begin is a cave. Protected from the elements. From there they can support viable operations on the surface. They are going to have to terraform that planet, so they have to build a whole new biosphere. Probably at least 500 years for that. They need to change the atmosphere from carbon to an Earth like nitrogen - oxygen atmosphere, and begin the rain cycle. That means they need off gassing plant life on a massive scale. That life will like have to be built in domes to support it, across vast areas of the planet. Plants like carbon, and Mars has plenty of that, but they need water, and we are going to have to manufacture it ourselves. We may be able to build eco domes with an internal rain cycle. Then just copy those. We can off gas the oxygen out of that. Leaky domes, if you will. Get enough of those going and you get atmospheric rain, and also lightning to make nitrogen. Get that started and plant life can spread on it's own outside. Then, eventually, you have a second Earth.