NikonD50 - I cannot get the lense to focus when taking pictures of my son playing football. Got some great pcitureslast year, but this year they are all out of focus, manual and auto focus. DoI not have the settings correct? Cannot find step by step instructions for the lense. The camera is pint and shoot. What is up with the lense? I remember it being that easy last year. What am I doing wrong? Should the lense be on macro?
Please help

Cameras - Sigma - AF 70-300mm f/4.0-5.6 DL Macro Super Lens for Canon-EOS