As mentioned previously, one of the reasons catch scratch is to mark their territory so the scratching post should be placed in an area that is well used and not hidden away in a dark corner. Once you've got your cat merrily scratching away at the post and not your furniture, you can move it somewhere else, such as the corner of the room, but you'll have to do this bit by bit.
Encourage your cat to use the post by enticing them with attention and things they like. Try leaving a few cat biscuits near the post or rub catnip on to it. Play with your cat near the post, try dragging something for them to chase up the post to encourage them to dig their claws in to it. Ensure you reward your cat when they use the post, they'll then associate the post with treats and affection and will be more inclined to use it. Many cats love to scratch when they first wake up in the morning so it might be an idea to have one in the room they sleep in.
At first you may find that your kitty is reluctant to give up their old favourite scratching places. Try and discourage them by covering the area with either double sided tape or tin foil. Cats really don't like the feel of them. As mentioned previously, cats also use scratching to scent their territory to try and get rid of this. You can buy all sorts of different pet odour removers from supermarkets or pet shops or you could use citrus scented sprays around the area as cats really don't like the smell.
If all else fails and your kitty still insists on scratching the furniture, try squirting them with a water spray or clapping your hands loudly and saying 'NO' in a firm voice. However, to be effective, you have to do this when you catch them in the act so they associate scratching that piece of furniture with getting wet or that sharp noise.