I am a new user, I have downloaded SMOS data with NC format,now I want to use SNAP to access the information(such as latitude,longitude,soil moisture and Frequency interference，etc. )from SMOS data,and export data in text (or other I can read)format, what should I do?
You can simply chose the format your want from the menu File / Export
There are several tool to inspect the data visually.
There is also a grid point exporter which you might want use.