Create an URL link in the pop up of a layer in Arcgis Online

[Marie-JoëlleDesgagné]

Hi

Here is what I am trying to do:

Every polygon of my layer has a lot number. When I click on a polygon, I want be able to press on an url. By clicking on it, I can create an attribute of another layer (ex. septic tanks) and in the attributes, the lot number is automatically added. How can I build this url? 

Ex: I click on the lot and them the url

By clicking on the URL it opens ths layer i'm interested in and the lot number is added automatically:

Thank you in advance !