Petfarmer's right, you have to have been working there for 28 days, then you can pick them up (you have to sign for them). If you need them before then for visitors, you can always try to strike a deal with someone that's been there longer and trade them - they pick theirs up, and when you pick yours up you give them back. Or if you know you'll be needing more than just the 4, you can buy discounted tickets without a delay, I think.
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PO!NT OF VIEW - A Different Look at Roller Coasters
http://www.crosswinds.net/~justmayntz/thrills/