It is the responsibility of your lieutenant and captain to train you for leadership in XG, if that's what you wish to pursue. The training itself will take place over time, but most of it will come after you are promoted to Lieutenant.
Our stance in Xiled Gaming has always been that promotions are earned, and for a Sergeant, that means adhering to the Honor Code, participating in clan activities, being active on the forums, and showing leadership potential. That last part is difficult to describe, either you got it or you don't.
If you're looking for a head-start on basic leadership skills, you can read over this post I wrote about a year ago:
http://www.xiledgaming.com/showthread.php?152184-How-to-be-an-XG-Leader