I'm trying to have my landing Page HTTPS. In this link https://help.salesforce.com/articleView?id=mc_es_create_landing_page.htm&type=5 it's said that there's a check box where you can select the page to be HTTPS, but when creating a new landing, I cannot see this option. Does anyone know where can I find the mentioned checkbox or how can I secure my landing page? Thanks
You can request an SSL certificate from Salesforce, which will be applied to a.o. your Cloud Pages - when you have applied a Sender Authentication Package, and using your own domain for Cloud Pages. This is a paid feature, which can be requested from your Account Executive. You will need two SSLs to secure all your resources: one for images, another for all other URLs. Please see this page for more details.
If you are using the default domain (https:// pub.STACK.exacttarget.com), and not your SAP domain, you should have an option of selecting HTTPS when creating a new landing page: