Assuming humanity found a planet they could travel to and was suitable for colonization, how would scientists re-engineer the human colonists for life on this new world?

Planet details:

It's slightly smaller than Earth with 21.5 hour days.

The gravity is 0.7g's.

It circles a red giant, so very little UV but it's close enough to get a fair amount of heat.

The atmosphere is not as thick as Earth with a lower oxygen content, but is still breathable. The 'sea level' air pressure would be about the equivalent of 2,000 meters above sea level on Earth.

The temperature varies widely, with the equator reaching an average of 50 degrees Celsius in the daytime, and an average of 20 Celsius at night. The poles in summer have an average of 30 Celsius in the summer, and 5 Celsius in winter at night it goes below zero and light snow occurs.

The humidity ranges from about 70% during the summer at the poles to as low as 2% at the equator. Water is scarce outside of the poles, with oases, springs, small streams and a few large rivers fed by the combination of mountain springs and rains caused by orographic lift, that eventually form salt lakes and brine marshes in endorheic basins, or dry up leaving vast salt flats along with other mineral run off.

The poles have broad, shallow endorheic seas that are similar to the Caspian, starting out relatively fresh at one end where the majority of the mountain run off comes from, turning salty in the middle and on the far end turning into brine swamps. Frequent rainstorms particularly in the winter keep the surrounding region humid and well watered.

The equivalent of algae and lichen form the major base of the food chain, and create most of the oxygen, using the salts and minerals for growth. This consequently helps to make the water somewhat fresh for animal life. There are plants as well but outside of the mountains, poles, and rivers they are few and far between.

Most plants are inedible and even poisonous, although some could be used for spice and filling without causing much if any distress to the digestive system. The animals could possibly be used as a famine food, if well cooked to break down the protein bonds.

So with a few decades to prepare the planet for colonization, what exactly would the scientists do to the colonists to help them survive and be comfortable on the planet?