Let's say I've managed a way to generate addresses, sent some btc, not I have Bitcoin Address and private key. How do I withdraw btc using private key? It is possible, isn't it? I was trying to do it through blockchain by adding the BTC Address to Watch List and I tried adding private key but I'm getting errors.

Thank you.

Anyone?

Greetings.
I'm trying to implement bitcoin wallets to my site. I figured out how to generate addresses with private keys. I need suggestion, instructions, tutorials... everything that might help.

I just got interested in btc development.
I developed 2 websites:
1. something like gigs and ads site. Basically users should be able to transfer bitcoins to the site and be able to transfer bitcoin and withdraw them.
2. the other one is like satoshidice.com. Users should be able buy tickets at a certain price.
Thanks