If you use Shopify setting up tracking is very easy!

Simply login to your Shopify store account and click on 'Settings' and then 'Checkout'

Once you load that page find the box called 'Additional Content & Scripts'

And then in this box paste in your conversion tracking code from WOW Trk. You will need to make one small change, on the end of the WOW Trk URL you need to add:
?amount={{ total_price | money_without_currency }}

An example is below:

<!-- Offer Conversion:Offer Name -->
<iframe src="http://t.wowtrk.com/Xz1c?amount={{ total_price | money_without_currency }}" scrolling="no" frameborder="0" width="1" height="1"></iframe>
<!-- // End Offer Conversion -->

NOTE: This will only work for stores which use GBP as their currency.