Welcome to the terraforming business, kid. Our crew will be stuck here for at least five years before the first colonists arrive.
Did you sign the NDA? Good. Then let me give you the basics of our operation here.
Stage 1: Surveying.
Geological surveying shouldn't take too long. The geology of most exoplanets in their stars' habitable zones is actually ridiculously earth-like.
Liquid water, plate tectonics, similar soil compositions, not to mention near-identical gravity and average temperatures.
Aside from working out the exact numbers for the maps, we don't really need to do much.
Stage 2: Oxygenation.
The atmosphere is a separate issue. Some people don't know this, but oxygen only became a part of Earth's atmosphere when photosynthesis first evolved 3 billion years ago.
Most earth-like exoplanets have a native atmosphere of carbon dioxide and methane instead,
and we'll have to replicate the oxygenation process artificially by releasing genetically-engineered cyanobacteria into the waters.
Then we just wait a couple of weeks until they clear up all the methane and fill the air and the seas with oxygen.
Stage 3: Cleanup.
The cleanup is actually the hardest part, the one they don't tell you about in the ads.
You see, while oxygen is crucial to the survival of aerobic lifeforms like us, it's highly toxic to lifeforms with alternative means of respiration.
If you were to breathe, say, methane, the sudden shift in oxygen/methane levels would turn your organs inside-out.
Long story short, most people think we never encountered any intelligent life beyond Earth,
and the last step is to make damn sure that no-one ever finds anything suspicious enough to make them think otherwise.