Did I screw up?

I thought I would try a cheap external flash to see if I could get rid of the shadows in my indoor shots. Note shadows in the pics.

There are only a few ways to kill shadows. The ones I know.

#1 move the subjects away from the background.

#2 Add more light to brighten the background

#3 soften the light

#4 move the light to a higher angle away from the subject (usually requires two lights)

None of these by themselves will completely get rid of shadows it usually takes a combination which why the more lights the better. Remembering that reflectors can substitute for lights in some circumstances.

To soften the light, one needs to make the light appear MUCH larger than the source. This can be done with large reflector panels (these could be ceiling or wall surfaces or they could be portable), umbrellas, softboxes, etc.

1)Direct flash, outdoors, will help reduce harsh shadows on faces from the sun.
2)Direct flash, indoors, will CREATE shadows on walls and other objects behind your subjects.

Did you try bounding it off the ceiling?

The 18-55 also isn't too good with grain. I can't see your settings, but pink skin against a pink wall is just, well, not very flattering.

One more! Bounce the light off the ceiling or a nearby wall. Use a card as a catchlight behind the flash head to throw some light directly on the subjects at the same time.

Time to get a nice bounce flash. 430ex if you can afford new, or 420, even 380ex, if you're looking used.

as everyone says, get a flash that can bounce (430ex is great, and <$250), but also get a sto-fen omnibounce, those tend to help you out a bit.

Wedding pros put their lights on brackets positioned DIRECTLY OVER the axis of the lens, no matter the camera orientation. It causes the shadow to fall DIRECTLY BEHIND the subject where the lens will not see it!