FOSS gamedev and creative worlds

I want to play MT with other players,but i don't know how to connect to a server. How to do that ?

select the "client" tab in your minetest menu.
make sure the "public server list" box is activated (it has a mark in it).
select the server you want to play, enter your playername and password.
(the password you use for your first login will become your password for that server, so make sure you remember it)

Ok. How can i make my world to play with other players ?

Just make sure your internet router forwards incoming connections on port 30000 to your PC running minetest. Also, click the "Public" checkbox (or set server_announce = 1) to display your server on the master list.

Alright, thank you :)