The manual hould tell you how as I cant remember exactly, but to charge it I suggest you select the Lipo balance program, and once there you need to tell the charger how many cells your battery has (3S in your case) and then the charging rate. In most cases its best to charge at 1C, so for the yuneec battery this will be 5.4A.
I have a basic guide which covers the basics you need to know about charging batteries you might want to read: