–There is a 'standard' error that many people make when using the Canon flash system. For indoor pics, they set Av, or Tv and expect good results.
Those two modes are used for fill flash (read the manual for full description). Therefor, the camera will not adjust the exposure nor shutter speed to allow for the light from the flash. The result with Av is a long shutter speed and blurry subjects.
Here is how to do indoor flash. (ie, not fill flash)
Select Manual mode.
Set Av, f5.6 (vary this up or down if you want)
ISO 400 (Vary this if you like)
Flash exposure compensation – select + 2/3. Note your results on the histogram and vary this if you need to.
Set the flash to ETTL. Use bounce flash or direct.