Hold the model such that you are looking at one carbon and the other carbon is directly behind it (through the C-C bond). This is the perspective of a Newman projection. Rotate about the carbon-carbon bond until the carbon-hydrogen bonds of one carbon atom are aligned with those of the other carbon atom. This is called the eclipsed conformation. Below is a partially drawn Newman projection, representing the front carbon of ethane. Add in all substituents. Draw the Newman projection of the eclipsed conformation.