Machine polarity settings??
DCEN
Electrode Negative for Flux Core Wire ??

Input power, 120 or 240vac ???
NO Extension cords??

Have you consulted the settings chart in section 5-3 of the manual for fluxcore wire??

http://www.millerwelds.com/om/o239988j_mil.pdf

Again... I would urge you to practice on scrap FIRST..