Minecraft add player to team based on scoreboard score

The command for adding players to teams is:

scoreboard teams join [teamname] [players]

And the code that means "all players" is @a

That means, to add everyone to a team we do

scoreboard teams join <teamname> @a

All we need to do is add a modifier to @a to accomplish what you want You had it right, but you were saying when there score is a maximum of one. This is the command you would use:

scoreboard teams join Rank1 @a[score_ranklvl_min=1, score_ranklvl=1]