Firstly, clean the spot with an enzymic cleaner (this gets rid of the smells that WE can't smell but dogs can).
Then, you need to encourage your dog to go outside (or where you want!). Use praise to do this AND, most importantly, set your dog up to succeed by taking him/her outside as often as you can (particularly just after eating/drinking). Every time your dog urinates in the place you want - then praise praise praise! You might even want to give them a little treat. If they go where you don't want, ignore them (don't punish them - it doesn't stop them going - might teach them not to go in your presence - or teach them that you are mean! but they won't learn much else - oh, however if you catch them in the act - you can go "uhoh, and take them straight outside. If they go then you can praise.).. Accidents inside should be cleaned with enzymic cleaner and you should just say to yourself "oops, thats my fault, I forgot to take him/her to the toilet spot in time". You need to teach your dog that it is GOOD to go to the toilet where the boss says. Then you have a dog that wants to go outside because that gets them a reward (affection etc). Dogs want to get good things and avoid bad things!
I have a dog that wags his tail after going to the toilet! AND, I haven't had an "accident" in the three years I've been in my house. Even if he gets sick, he will actually wake me up to ask to go outside. Its all from giving him positive reinforcement for going to the toilet where I want him to.
Good luck!