Could someone explain how the score sequence works for an xwing tournament , or maybe suggest a link I could read , many thanks .

'Score sequence'?

How do you mean?

Either way, it's all clearly explained in the tournament regs.

https://images-cdn.fantasyflightgames.com/filer_public/d1/88/d1884752-34e1-4ad6-a992-824f41694a03/x-wing_20_tournament_regulations_printer_friendly.pdf