Dividing the word is going through and pulling out the truth. Dividing the true promises of God’s Word out from the scripture, where a misinterpretation or a misunderstanding could steer you away from his promises.
But, Dividing goes with everything in your life, a Christian should rightly divide their lives so that they can pull out the truth, and be able to tell truth from lies, in every aspect of their lives. The truth is the rock, the good stuff, and to divide it from the sand will help you to have the strong foundation that keeps your life steady.
Hope this helps. 
P.S. The Helper can aid the Believer in all of these things.