To assemble this 608 bearing, you need the following parts:

1x innerring
1x outerring
1x cage
1x assembly helper
6x steel balls diameter 4,5mm

For the printing settings, I recommend setting the seam position to random. This will prevent a very pronounced seam in the ball track, which would impair the roundness of the bearing.

Assembly:

Place the outer ring on the assembly helper and insert 6 steel balls. The balls should lie on the small shoulder in order to be pre-positioned in in the center of the ball track.

Carefully insert the inner ring without moving the balls.
The assembly helper should be held slightly in place.

The balls must the be carefully distributed evenly with a small screwdriver and then the cage only needs to be clipped in.
The ball bearing is the successfully assembled.