Your initial location isn't very good. You start with only a handful of survivors and the only buildings that you have are a reactor and a Gathering Post for your resources. All of the survivors are homeless. However, this is issue is not your priority. You can't build tents, the most basic and cheapest of houses, outside of reactor's zone.
The first moments - get some coal!
You must ensure resource deliveries. Focus especially on getting coal. Hire the maximum number of workers on a selected coal pile. This will give you enough supplies of this resource. Wood is also important, it is used for building and is necessary for researches. You should hire at least 2/3 of the maximum number of workers to get it. Initially, it is useful only for creating more expensive buildings that are cold resistant. This resource will be needed in bigger quantities later.
A reactor is your colonies' center of life. Start the machine when you get enough coal. Initially, it will only create a small area of heat. Use it to build tents, medical posts and cookhouse. Avoid placing buildings that doesn't require heat in this area.
All buildings must be connected to a reactor. Because of that it is important to expand your roads. It is also important to make roads that lead to the resources that you use. Otherwise, your workers have to go through snow which slows them down. This lowers the rate of extracting them.
Providing food for your citizens is also very important. In the beginning you have a given amount of food that must be prepared in a cookhouse. However, those supplies won't last for too long and that is why you must build hunter's huts and hire the maximum number of workers. You should also issue the "Soup" law from the book of laws. It reduces happiness but it unlocks a more efficient way of preparing meals in cookhouse which eases a risk of starvation.
Starvation and cold are the basics dangers at this point of the game. You must check regularly whether you have enough supplies or if you generate enough heat!