I'm not an expert on the issue, but since the patents and trademarks legislation is similar in most countries, you probably have to register you mark, signs and slogans with your closest office of “Marcas y Patentes” in Spain. Also I think you have to place the Trade Mark or Registered sign next to each name, logo or slogan you use. That should make 3rd parties aware that those names, logos and slogans are your creation. However, the only purpose of this is that you can sue the other party once they plagiarize your trademarks. But that kind of litigation is costly and hard to proof for small companies. So I would say that if your business is not legal or big enough to pay the services of a trademarks and patents lawyer, then forget about it.