An appropriate statement could go something like this:
SPC Snuffy, I would like to congratulate you on your appointment to the position of squad leader. Your two responsibilities are to accomplish the mission and look out for the health and welfare of your squad.
Then the counseling should closely follow an initial counseling for a squad leader.
Check out the book the Mentor for sample initial counseling statements. It can be found on MentorMilitary.com