Breakpoints with C++

Hello 4chan, 7chan failed me in this..

I want to create my own debugger, like OllyDBG but as a injected DLL-file.
I have all functionality I want except for one; I don't know how to set/place breakpoints in the code..

My google-fu has failed me in this, if anyone could help me, please do! :)

BTW, just so you know, when you press F2 in olly to set a breakpoint at a memory address, all it does is it write an 0xCC byte at the address.