Kathy...
If you want to shoot waterfalls that look creamy, use a slow shutter speed. Use the lowest ISO of which your camera is capable and the smallest aperture (largest f/number). This will proide the slowest shutter speed. You will need something on which to brace your camera because at slow shutter speeds, camera shake can be a problem. A tripod is best but anything sold will work. use the time delay to fire the shutter so that your finger pressing the button will not cause the camera to move.
A neutral density filter is often used to slow down the shutter speed even more but, that is a bit advanced for a beginner.
As far as landscapes go, don't have the horizon cutting directly across the center of your frame. Instead, run the horizon across the botttom or top 1/3 (approximately).
Use a tree limb to frame your shots when possible and to give them depth.
If you can afford a decent circular polarizing filter (CPL) that would help in many shots. However, decent ones are somewhat pricey and cheap ones can ruin your image quality.
Use a lens hood. If you don have one, that is something you need to buy! Chnese knock-offs from eBay are just fine. I use a Chinese knockp off on my thousand dollar + 17-55mm f/2.8 IS lens and it works just great.
For general shooting, set you ISO at around ISO 200. Set your f/stop (using AV) about 2 stops smaller than maximum and shoot!
Shoot lots and lots of images. Shoot from different angles and directions. The great thing about digital is that the shooting is free after you initially purchase the equipment.
Get a decent editing program if you don't already have one...
Do a Google search for "Landscape Photography Tips". Lots of neat sites like this National Geographic:
http://photography.nationalgeographi...tography-tips/