My first outing with the 6D

An exemple : if I aim at my iMac with the little black Apple right in the center point, it Will most likely be an outer point to catch the border of the computer.

and this morning I have a dirt (dust) on my viewfinder. Not à big deal since it will not come on the picture but for a 1 week old camera, this is not funny. Any easy way to clean that ?