Look at this picture – a demo shot I made during a recent course, to show what not to do.
Can you see what is wrong here?
Yes, her eyes and face are all shadowy. Becuase I aimed my on-camera flash straight up. I see many people do this; it is seldom a great idea. Instead, of course, aim it behind you:
Note you need to have some kind of ceiling or wall behind you above that will reflect light. You may need to go to a higher ISO; in a large room, much higher, which is fine nowadays.
You can drive this “the umbrella is where you aim your flash” thing to extremes. Aim at the floor for eerie light – simply rotate your camera upside down, and you get:
Nice warm floor reflection!
Now, to see how fine modern cameras are with regard to ISO: a camera like my 1Dx goes to ridiculously high ISO values. 51,200 ISO with some noise reduction in Lightroom:
Yours will probably not be quite as good, but no problem if you want to go to a higher-than-usual ISO. Do it, and live with the grain – better than bad light or motion blur!