After decades of floating through space, a ship with the remnants of humanity in stasis arrives at a distant planet that looked like it could support terraforming only to discover that it not only has life, but it's sentient and has a World War 2 level of technology. There are several different alien governments that currently have fairly friendly relationships. Our protagonists park in orbit behind a gas giant and think about what to do. They need to somehow set up a human civilization on the planet. They have about 1,000 humans, a power source that won't run out anytime soon and the ability to manufacture just about anything at a small scale of production. How should they go about dealing with the current inhabitants and beginning colonization?
This relatively small ship does not have the resources for an Independence Day style invasion and any straightforward attempt at contact would result in being wiped out.
Some more details about our would-be colonists/invaders. Earth is gone, there will be no backup, and they don't have any other potential systems to go to. The people on the ship are all experts, so it's not out of the realm of possibility that they could send cloaked ships to the surface for reconnaissance, create robots to infiltrate existing society or rework the biosphere. They have time on their side, but are pretty desperate.
As for the aliens, I would expect them to freak out if the situation isn't handled delicately. If humans are captured, they can expect to be kept in an area 51-esque facility and have their technology thoroughly examined. The nations on this planet have a tenuous peace, so there is plenty of potential to muck with their politics.