Get a decent photographer to take some good but not too artist shots of you (formal, casual, swimwear and underwear) make sure they don't forget a hand and barefoot shot.
Put together your portfolio, nothing extravagant (less is more) and send it to agencies. You'll start as freelance, but with some luck, an agency might want to exploit you (make no mistake and look very closely the contracts agencies might offer some are close to indenture)
Good luck