I'm not quite a real bass player, but I play it very serious and "real bass player" - like.
I've seen many guitarists playing bass guitar. Exactly the same way as I play guitar too. The finger position and the diffrent plucking technics (right hand) are totaly diffrent from a guitar.
If you have a musician ear and you hear the chord roots going up und down, you are very fast to be a good bass player. Unfortuneatly, it takes long time to hear what going on in a song.
If you prefer to practice slapping, you probably have to take lessons, or by the way there are also some good online slapping lessons...
But for all instruments, you have to practice and practice and...
In the beginning it hurts a bit when you strike the string with your right hand. But you'll get used to it.
What's very important: Play loud! I mean not to turn up your amp (I can imagine, you could...) but to hit the strings hardly. I've seen bass players, playing very well but they don't have a nice attack.
Try also to have one finger for each fret on the left hand. Start practicing in the middle of the neck, where the frets are closer. Then, start going to the left, where the frets are wider.
Just to note some points of all the others...
Search a band, where you can play and keep staying on bass, on don't change your instrument very month....
Lukas
Sorry for my english...