First focus on tactics and pattern recognition by playing many games. Basic opening theory is all that is required at your level.
The large databases can be found online and are happening in current tournaments where top level GMs use novelties in established variations to surprise their opponents.
Most seem to use ChessBase and keep it up to date with the latest tournament results. Non titled players can get by with any number of cheap (or even free!) databases, often bundled with engines. Software like Fritz, ChessKing, or HIARCS all come bundled with DB's. There's another big one that a lot of pros, especially Russian use, but I forget the name. You could probably look it up...
I see that in many large tournaments grandmasters talk about their preparation against their opponent using large databases. What databases do they use and how could I get it?