KM3NeT is a research infrastructure aiming to study astrophysical sources as well as to perform particle physics studies, through the detection of neutrinos in the abyssal depths of the Mediterranean Sea. The KM3NeT/ORCA detector (Oscillation Research with Cosmics in the Abyss), currently under construction, is deployed at 2450 m depth near Toulon, France. It consists of vertical structures (Detection Units) equipped with spherical Digital Optical Modules, each hosting a set of photomultiplier tubes capable of detecting neutrino events from the Cherenkov radiation induced by the daughter particles. In this contribution, an analysis of data collected with the first 6 Detection Units (ORCA6) leading to a sample of atmospheric neutrino events is described. The angular resolution and the energy reconstruction performance for this event selection, which is a key factor for measuring the atmospheric neutrino flux, are also presented.