Make sure to set you game up so the goal limit is 15, so you'll have the maximum amount of chances to gain this.
To get power ups you need to check your opponents. The powerup required for this is a bright green +2, the game announcer will also call it out when you pick it up. While you have this power up score 2 goals with the player it is attached to. You can not do this with just one Double Up Powerup, since your powerup goes away after a goal. So pick it up again to gain the second goal. Also, see the "Juggernaut" achievement for tips on scoring goals.
*This can be boosted with a second controller or online*