How to host a public lobby?

I join the R class lobbies but the thing is I like racing with manual transmissions but so far all the lobbies I am joining only have automatic transmission set up and I can’t change the option because it says that only lobby hosts can change the options. So I wanted to know how can I set up my own public lobby so I can change this option when I race? I see I can set up a private lobby but I just want to play with random people.