You just make a account with a username.and then you need a server ip and if your friends are all on that server you can play with them.

But how do all that? How do i invite my friends

1: you need to go on minecraft.net and register an account

2: you need to get the paid version of minecraft, click buy now after making an account on minecraft.net

3: you need to find a server to play, or create your own for just you and your mates

4: once you found a server or created one, send your friends the ip and they will join the server

5: once they join, meet somewhere and make a base, thats all you need to do

stuff needed:
minecraft premium account
server to play on
or have your own server

need any more help add me on skype: kieronshorty

Ok, first and foremost, you must create a account here: [ Register or Signin to view external links. ] the register button is in blue letters in the top right corner.

Once you register, you must then buy the paid version (full version) as seen on the front page. The price is somewhere between 20 and 30 US Dollars.

Download it and login and you are all set to play!
To play with friends, find a server you like on here, or on a forums dedicated to minecraft. Enter the ip given into the multiplayer section on the minecraft menu. Give your friends the ip and you will be connected and able to play together!

You can host a server for free if you download the server from the minecraft website. BUT you can pay for a server if you have horrible internet connection.

And no, you do not need steam to play.

Hope this helped!