there's really nothing that can be adjusted on that telescope. It's just a very low-end telescope with cheap optics and eyepieces. The lenses are likely just plastic. The only really usable eyepiece would be the 25mm, in certain conditions the 10mm might be of use.
I also started with a telescope like that before moving into the real quality telescopes. I was able to view the Moon, Saturn, Jupiter with any good success. But with Saturn being low on the horizon in the evening, it would likely be not very sharp. The 675x power while using the 4mm and 3x barlow is achievable theoretically, practically no way!!
Hopefully you didn't spend a lot on it.
Manual
http://www.tasco.com/products/manuals/46060675_TML-722.pdf
Some background and hints for Tasco telescopes.
http://www.rocketroberts.com/astro/tasco.htm
More information
http://www.astronomyforum.net/refractor-telescopes-forum/621-tasco-galaxsee-675x-refractor-telescope-help.html
Hope this information helps.