Copyright has nothing to do with team names. A team or company or product name would be a Trademark. What you need to do to protect a Trademark depends on local law (so talk to a lawyer) and, more importantly, what the Trademark is actually worth.

If your "Team" is a registered company undertaking a commercial venture then it is likely worthwhile protecting it because you don't want another company using the same name. If it is a bunch of friends making a game for fun that will likely be downloaded by 100 people total then it would be a waste of money.

Basically a trademark is a mark used to trade. You don't have to do anything to protect it other than trade - the law automatically provides protection except that you would probably need to pay a lawyer to take action against anyone using your trademark (which is why I said that it isn't worth worrying about unless you are a real company with something to lose). You can register a Trademark (how to do so and how much it costs will depend on local law) and this may provide some additional protection - however it costs money so you have to decide if the extra protection is worth the money.

To better understand trademarks read this Legal overview article. I suggest you also Google for your countries own copyright/patent/trademark office.