you have to understand how hamachi works first.
To make it short, it tricks your OS into thinking that there is an lan connection that there isn't. The connection to the hamachi network. So everyone you need to connect to with hamachi, need to be on the same hamachi network, think of it as being on the same lan. If they don't have hamachi and they are not on the same hamachi network, then they are not in your lan, meaning they can't connect to you.
So tell them to get hamachi and then join on the same network and it should work fine, and I wouldn't bother with any other similar software since hamachi is great.