Okay so it works putting the link in the file DrByte said to
but I need to be able to have the order number and total sent to the site aswell
I have put the tracking pixel below if someone can help me with what to do next that would be excellent

<img
src="https://site.com/sl/pid=254&ot=ORDER_TOTAL&on=ORDER_NUM
BER/sl.gif" width="1" height="1">

I need something to go in the ORDER_TOTAL and ORDER_NUMBER