How do I Buy EOS from eos.io

I came across the eos.io site to buy the eos token, but after reading through the site on how to register the public key, claim the token I still can not find my way around it. I use an imtoken wallet and I can access the wallet address and the private key yet still can not find the public key and where to register it. If there is a easy step by step way anyone can show me I will be grateful.