I'm not familiar with the SR devices today, but when I bought mine a year and a half ago it came with an antenna about 4" long that screwed into a port on the back side of the box, near the power plug. (There was also a stubby 3/4" antenna that I think was for the wifi.)
Once paired to your iFly, you will only get radar imagery in the Weather mode (Mode > Weather). This mode is similar to Vector mode in that there is little in the way of underlying map data...it's mostly just outlines of major airspaces and dots where airports with weather reporting stations are. The airport dots are color-coded for VFR, MVFR, and IFR conditions, and if precip is in the area, you'll see green / yellow / red pixels representing radar echo intensity.
These airport color-codes and radar echos are NOT overlayed on any other maps (IFR enroute, sectional, etc.). You must be in Weather mode to see those data.
Note also that tapping on the map while in Weather mode will pull up text weather (METARs, etc.) from reporting stations near where you tapped, and these text data are also regularly updated via ADSB.