Ok so i think you know how to create a server, but people cant play on it.
Two possibility :
1) sv_lan= 1 on your server.
2) you router is not configured. if you have two or + conputers on internet you have to configure it.
but if you have only one computer on internet you can disable it (i did it).
But if you dont know how to create a source dedicated server :
1) Download source dedicated server with steam.
2) Launch it.
3) Select internet (the name,the rcon password...)
4) If the ip of your server is 192.168 something, you have TO CONFIGURE YOU ROUTER OR DISABLE IT.