(hope I'm not invading or anything)
I took 2 years of Japanese in high school when I was a Freshman and Sophomore.
The best way I figured out how to build my vocabulary was to learn all Hiragana before anything else and learn how they go into different words, etc. A while after I learned most/all of the hiragana symbols, I would write as many as I could remember down, and then keep testing myself until I could write them all down in one session without missing any.
After that, I'd work on building my words. I would practice with these cards that had different words on them, mostly consisting of 2 - 4 hiragana symbols, and try with different cards on different days to remember as many as I could. After a while, it comes pretty natural and it's pretty simple to start wording out sentences and understanding people talking in Japanese. I still have problems understanding most Anime shows in Japanese, though. It takes a lot of time to get to the level where you can understand a lot.
But yeah, I'd suggest maybe buying a book or something to help you, makes it a lot simpler to understand everything.
Sorry for the long response, by the way, just thought I'd share.