How to make scoreboard points?

Solution 1:

1. Setup a scoreboard for both teams:

   /scoreboard objectives add OBJNAME dummy
   /scoreboard objectives add OBJNAME2 dummy
   

Change OBJNAME to any name you want it to be. Don't change "dummy".

2. If team A wins, add 1 to the objective 1. Team B, add 1 to objective 2.

   /scoreboard players add @a OBJNAME 1
   

Change the OBJNAME to either team A/B as you made above. Don't change number 1.

To see when a team wins, you need command blocks with testfor command:

/testfor @p[score_OBJNAME_min=3]

Put that again in another command block with its other OBJNAME. Put a comparator on that command block and then another one to do whatever you want when a team gets to 3.