An important thing is to realize that "675x" is a lie. I don't know the exact size of your telescope, but I suspect it's similar to the 60 mm refractor I had as a kid.

A 60 mm refractor is 2.4 inches across. A rough rule of thumb is that the maximum usable magnification is 50x per inch of aperture, so don't use a magnification greater than 120 (more or less).

The magnification of a telescope is given by the following formula:
mag = (focal length of objective)/(focal length of eyepiece)

The eyepieces should have focal lengths written on them. The telescope probably has the objective focal length listed on the tube -- perhaps 600 mm, or something in that ballpark.

If your telescope is like the one I had, it comes with a barlow. You probably shouldn't bother with it, because it will just give you an excessively high magnification, which in turn gives you a big blurry image.

Some general guidelines:
1) Always start with a low-power (high focal length) eyepiece, and work your way up to higher power if you want.
2) Make sure the finder is aligned. This might be easier to do during the day. Put a low-power eyepiece in the telescope, and point it at a distant object (such as a distant telephone pole). Center the object in the telescope, and then adjust the finder so the object is centered there as well.

A telescope like this is not great, but you can still get nice views of some objects:
- moon
- planets -- particularly Saturn and Jupiter
- wide double stars (such as Albireo in the constellation Cygnus, which is high in the sky in the summer, or Mizar in the middle of the handle of the Big Dipper)

Currently, Saturn is high in the evening sky. The crescent moon will become visible in the western sky starting Monday, April 7. (It will be visible with difficulty on April 6, but much easier on April 7 and each night thereafter.) Jupiter rises after midnight, and will be well placed in the evening sky starting around late June this year.

And if you want to look on the bright side: You should be able to see the rings of Saturn, and that makes your telescope better than the one that Galileo used. (He saw them, but never clearly enough to see they were rings.)