Well at first you should realize (I assume you do), that chess is amazingly complicated game. In order to actually master it you need to devote yourself completely for years. I've been playing professionally for around 14 years now, and I cannot say that I am even close at being very good at this game. Probably better than 99.5% of people in the world, but.. I brought that up cause I know some people, who think very highly of themselves, or just cannot stand to not being able to do something, so they pick up chess and think they can master it in a matter of days or weeks. That never ends well for your ego
As long as you realize that and still want to become better at chess, a couple tips:
1. Always take the games you play seriously. Try learning something from every single game - even if you won a game, it does not necessarily mean, that you played well. If you got beat, analyze why did it happen. So the best tool that chess players are using to improve is the analysis after the game. You should learn the chess notation and write games down, so you can replay them later (or you can try memorizing it).
2. If you are really interested in it, try going to your library and getting some chess books. Yes, in our computer era you can probably find everything online, but believe me, it as a completely different and better feeling, to read from an actual book and make moves on an actual board, instead of a computer screen.
3. There are also tons of chess websites around. I cannot say I know a lot of sites that provide training cause I never really looked for it, but I am sure you can find some via google. If you are interested in seeing how better players play, you can try
www.chessgames.com , it has a pretty big database of games that you can replay at any time. Also, there are tons of training video's in Youtube. Try looking for user "grobchess" , that's a friend of mine and I am pretty sure he made a decent amount of instructional videos.
If you have any other questions, don't hesitate
Hope that helps, good luck!