need help rooting galaxy s5 active

I need to root my phone as I am running out of Storage and the att apps are pretty big and I'm limited as to what I can move to my 64gb sd card. I have a galaxy s5 active (g870a) 5.0 android version 3.4.0 kernel I know I will probably have to downgrade but I need to know how and what programs and root tools. Thanks.

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