When you get a new Violin or Viola, you need to set it up correctly. This is especially true when you purchase an instrument online - instruments purchased online are normally shipped with the bridge flat against the face of the instrument so that they can be shipped.
How to set up you new violin or viola.
1 - place the bridge upright on the face of the violin or viola and position the strings.
2 - Tighten the strings. To make the strings stay in tune, you need to push the pegs into the hole very firmly or they will slip and the instrument will go out of tune. When new strings are put on a violin or viola, you need to adjust the tuning quite often at first. After the strings get used to being tight, you won't need to adjust the tuning as freaquently.
3 - Rosin the bow - with new rosin, it is often a good idea to rub some sandpaper on the smooth front of the rosin before you rub the rosin on the bow.