Internet Help please

[Beta Man]

I have a wireless connection to my Mac laptop..... I know little to nothing about this stuff, so take it easy on me

I always left my connection "Open" because I figured if neighbors want to 'borrow' my connection, no big deal.... as I didn't use it for file-sharing or big downloads etc.....

Recently I've gotten a Call of Duty addiction, and also have been streaming a lot of movies from Netflix to my PS3.... I want to increase the quality of the movies since they seem to vary sometimes, and also reduce the lag I get sometimes, or the random connection lost errors I get once every 5 hours of game-time or so......

How do I make my connection "protected" ???? My two immediate neighbors on both sides have internet, and they're the only two neighbors I care about anyways..... so I don't feel like sharing anymore

I have a 2-wire or something like that, if that makes a difference.....

Thanks, and sorry for the "Internet for Dummies" questions!