Integrate Leads with Facebook AdSet

Integrate Leads with Facebook AdSet

Hello, I have a custom form to insert Leads in my CRM. I get the facebook AdSetID from the url ( I can get the Ad_ID too if its necesary). I have installed  Facebook Advert Manager and add a facebook adSet lookup field in my Leads Module. 
I want to fill this field but I dont know how to work with the api. 

I tryed  <FL val="AdSet_Id">8960000000216197</FL> when inserting the Lead Record but didn't work. 

Hope you can help me.