Transfer Function

[#1]

Newbie here.. I am struggling to teach myself how to run a transfer model. I am trying to run a transfer function for sales with temperature being the input variable. 

After prewhitening the data- I have found lags at 5, 6, and 8. 

I am stuck on how to continue from here. Thank you for any help you may be able to provide. 

[#2]

Please check out this reference Time Series Analysis Any edition should be fine.

Look for the chapter on transfer function models. Pay attention to the discussion regarding prewhitening and impulse response. Look for a figure listing some examples of impulse response functions in that chapter.

Your plot here does not resemble an obvious pattern, so maybe you need to fit a bunch of different orders to find out the most appropriate one.