The representation of the cosmic microwave background radiation is an oval. where should I place myself in this oval, to behold this radiation around me, or else how is this projection composed?

Answer

The oval represents the sky around you, in galactic coordinates. You cannot indicate your own position on that map, because it is not part of it.
The horizontal line in the center of the figure is in the plane of the Milky Way. From left to right, therefore, correspond to 360° around you.
The top apex of the figure is the galactic north pole, so the direction perpendicular from the galactic plane to the right (whatever that is). The point at the bottom of the oval is toward the Galactic South Pole.
You can compare it with an oval world map, with the equator as the long horizontal axis, but made by someone who is located in the center of the earth.
The difference is: on that world map we can indicate our own point of view. Not on the oval of the cosmic rays. This map therefore indicates the intensity of three radiations when we look (in galactic coordinates) around us at the universe, in all directions. Although we see those directions as a spherical surface around us, we must somehow represent that in two dimensions. An oval is then a good choice.