No, you don't need any extra flux, you need the correct solder.
The solder you have appears to be a general purpose solder, the solder wire diameter is quite large 0.063" is 1.5mm, my thickest solder is 0.7mm and is intended for electronic use.
You need new solder and you do not need flux.
Buy the correct solder and the correct flux will be in the solder.
As for the RA flux and the solder you have already, save it for fixing something big and heavy like a water pipe.
JimB