Hiding part of a form based on dropdown selection

Hi guys,

Sorry if this questions has already been asked, I tried to look online for hours and don’t seem to be able to find an answer.
Basically, I have a subscription form, where I want the user to select something from the dropdown, based on his selection, the address input part of the form should appear/disappear.

If the user selects the first dropdown choice (Suis-je eligible), then the (Adresse) part should appear
I assume I have to use some custom code to achieve that, but I’m not too familiar with that.

Thanks for your help!
(Sorry the website is in French)


Here is my site Read-Only: Read Only Link