Copy the link and paste it into the address line at the top of the browser window.
Click in the line called 'Name' and write what you want the tournament to be called. There's a maximum number of letters so don't make it too long.
Now write a description in the next line.
Then choose the number of people you want to invite, and the group size. So if you have 8 entrants with a group size of 8 you'll have an all play all octet. If you have a group size of 2 you'll have a multi round duel.
Then choose the timeout period from the drop down box.
It's been a while since I created one but I think that once you've cricked 'create tournament' it will ask you to enter the names of the people you want to invite. They will then be sent a PM giving the password.