Hi, @Vaati, welcome to Emlid Community!
Did you follow the base and rover setup that Emlid makes available in the documentation?
RTKPOST only generates the .pos file as a result, in the WGS 84 coordinate system. You can copy the processing result (LAT, LONG and height) to a text file and use it in any software that accepts import in this way.
The columns sdn(m), sde(m) and sdu(m) are the standard deviations of the adjustment result.
Emlid Studio is a tool that can help you with your processing. It uses RTKLIB in the background. It is a more didactic interface to carry out your processing.