Where to place Captcha

[lazar_lazarus]

Hello guys, I am one of triers of this new OC4  thing. My store homise.ru as expected was bot-attacked. I dont know who those guys are who write those bots and for what reason. I am receiving spam emails with the same content on different languages every 10 minutes from different email addresses. I can't block this bot and what people advise is using Captcha. I got Captcha codes from Google, but don't know where to place them. Some html file? Will appreciate any help!